Crime Scene Investigation

Alternate Light Source

2009-02-26T09:50:00.009-05:00

Inspection with an alternate light source (ALS) is the second step of every processing technique in the FBI processing guide. It can enhance the visibility of a wide range of evidence. While inherent luminescence is secondary to visual inspection, there are certain forensic techniques that absolutely depend upon ALS.

There are several types of forensic light sources on the market. Many of the newest ALS units are designed around light emitting diodes (LED) and resemble flashlights. Older models look like a box with a flexible tube protruding from the side. In any case, the method of use is the same. An item is illuminated using a very specific wavelength of light while it is viewed through a filter. Inherent or chemical fluorescence often creates an intense change in contrast which is usually the desired result. Since there are several wavelengths of light that can be used in combination with several different filters, finding the best combination can be a meddlesome task.

In order to make life easier and encourage the use of a very effective tool, I have compiled the following information. Click on the chart to the right for a larger view. The left column contains the type of chemical process used on an item. The second column has the preferred wavelength for illumination with the background color defining the color of the filter. The third column lists the combination that produces the second best result. The last two columns show the filter colors that work best when blacklight or ultraviolet light is used as the light source.

These values do not reflect the only possibilities. They do, however, typically produce the best results without having to hunt through numerous combinations when the source of fluorescence is controlled.

Luminol Photography

2008-12-18T21:42:00.000-05:00

Luminol is a blood visualizing agent that is commonly used in crime scene investigation because it produces a chemical reaction with hemoglobin causing luminescence (glowing) wherever blood is present. It is usually used as a final step because it normally does not produce significant detail for pattern identification but has tremendous value as a locater of blood. Luminol is applied by spraying and can be a great resource when you are just trying to find traces of blood but don’t have any idea where to begin looking.

In the past, Luminol was only useful for finding blood traces because it would destroy DNA making any identification of the blood that you found improbable. This is no longer the case as there are certain variations of Luminol that are available that do not destroy DNA. BlueStar® Forensic was developed in 2000 and has become my personal favorite. It does not destroy DNA, it produces a stronger and longer-lasting luminescence, and it has a longer working life. While I still use it as a last step, it can often help me find the DNA evidence that I need.

Of course, everything needs to be documented as thoroughly as possible. This includes photography of the luminescence which is a tremendous challenge. The preferred steps for photographing Luminol have been to place the camera on a tripod, remove or turn off the flash, set the focus manually, use a remote shutter release, and use an automatic setting on the camera if available. This also requires that the ambient light in the area is restricted as much as possible. I carry a large roll of black plastic to cover windows and doors for this purpose. With standard Luminol, the photographs were never very useful and rarely showed any of the luminescence that I was able to see at the crime scene. Switching to BlueStar® Forensic made it possible to produce better photographs due to the increased intensity and duration of the luminescence, but the background was not visible. What I wanted was to photograph the luminescence as well as the surrounding area so that I could effectively document not only the presence of luminescence, but its location as well.

I have found that if there is some ambient light, Adobe Photoshop® can be used to enhance the original image. First, make a duplicate layer to avoid working on the original image. Then from the top menu bar, select Image > Adjustments > Auto Levels, some improvement to the background can be produced without reducing the quality of the luminescence. While this method tends to produce truer colors than other methods, it still does not clarify the background to my satisfaction in most cases and Photoshop can be a difficult program to master. If you choose to use this method, remember to save a copy of the file for court purposes and document each step in a report so that you can reproduce the results.

The problem with photographing Luminol is that cameras require light to operate but Luminol requires darkness to be visible. In order to illuminate the background, some light is required. Since Luminol produces a blue luminescence, the background can be illuminated with a different wavelength using an alternate light source. I have only recently begun to experiment with this technique, but I am gaining a preference for ultraviolet because it seems to produce a great deal of contrast to the blueish glow of the Luminol. When learning this technique, keep in mind that the amount of ultraviolet light required is very minimal since the shutter speed is going to be very slow. If you have a digital camera, take several pictures to help determine what the best direction and distance of the light source will be prior to applying Luminol.

Compact Disc Life Span

2008-03-03T17:10:00.009-05:00

Keyword Search: “How long will CDs last?”

This is a question that I researched extensively prior to switching to digital. The answers I found were less than satisfying. The problem stems from the fact that CDs are a relatively new medium, so information about long-term aging is not available. However, tests which simulate long-term aging have been conducted by several organizations in an attempt to determine the viable shelf life of CDs.

These tests provided some valuable data about the strengths of CD components. CDs have three main layers. The first layer consists of clear polycarbonate plastic. The second layer is a sheet of very thin reflective aluminum or gold. The third layer is acrylic and is the side that can have a label attached. CD-Rs have an extra dye layer between the plastic layer and the reflective layer. CD-RWs have a phase change layer and two dielectric layers in place of the dye layer. Plastic and acrylic have incredibly long shelf lives. Since the other layers are sandwiched between the two, they are well protected.

The tests also provided some valuable data about the weaknesses of CD components. Primarily, the method used to combine the layers. Separation seemed to be the main problem during the tests. There did not appear to be a significant difference between archival quality CDs and standard CDs during the testing. Also, since CD-Rs and CD-RWs have light sensitive layers, exposure to sunlight can cause degradation of the data on the CD.

Because these tests were designed to simulate the aging-process, facts about the actual life span of a CD have not been determined. Estimates range from a few years to several decades. I contacted several organizations that utilized CDs for long-term data storage and none of them had experienced any issues regarding the age of a CD. I have used CDs to store crime scene photographs for about six years and have not experienced any CD failures due to age. The most common errors are produced by physical damage to the CD and exposure to sunlight – just like 35mm film. I am not concerned about the shelf-life of CDs. My priority is on the care given to their storage – just like 35mm film.

What does worry me, however, is the speed at which technology changes the world. In the last few decades, computers have gone from 5 ¼” floppy diskettes to 3 ½” floppy diskettes to tape drives to Zip drives to CD drives to DVD drives…etc. I just need to make sure that I transfer all of the CDs to the latest format before compact disk drives head down the road toward extinction. I find it hard to believe that this will occur in the next few decades, but then again, who would have thought ten years ago that you could log on to your computer with a fingerprint swipe?

If you or your department is thinking of switching to digital and are hesitating due to the question of CD life, I would advise you to make the switch. Many photo labs are dropping their dedicated 35mm printers for equipment with digital capabilities. In my opinion, 35mm film will become obsolete long before digital media.

For more information about CDs, take a look at HowStuffWorks.com. There is a very informative article by Marshall Brain explaining how CDs work and another article by Tom Harris regarding CD burners.

Prints on Metal

2008-02-22T16:22:00.007-05:00

I received an e-mail from a person who asked for some possible solutions to a recurring problem. When examining metal objects like a pistol magazine for latent fingerprints, they could see a faint fingerprint on the surface that did not have enough contrast to photograph without additional processing. The problem is that none of the standard processing techniques improved the visibility of the fingerprint. Powder doesn’t stick, Cyanoacrylate doesn’t adhere, and other chemical techniques discolor the entire surface, obliterating the fingerprint.

Before presenting a solution, let’s discuss the problem. Powders and Cyanoacrylate require some form of moisture to produce results. Since powder and Cyanoacrylate are not sticking, then there must not be enough moisture left in the print. So why is the print visible? The answer to that lies in the type of surface. This type of problem rarely occurs on surfaces other than metal. The reason is that the faint fingerprint you can see on the metal is actually oxidation. Human oil and fingerprint residue contains salts and acids that produce a chemical reaction on the surface of the metal. This reaction consumes the natural moisture that powders and other techniques require to be successful but produces a slight discoloration that is barely visible.

Now that we understand the problem, we are better able to define a solution. In my experience, the method that has produced the best results has been side lighting. By holding a light at an oblique angle to the item, you can improve the contrast of the fingerprint. This can sometimes be done with a flashlight but an alternate light source usually produces better results. Since the wavelength can be controlled within a few nanometers, you can experiment with different wavelengths until you find the one that produces the most contrast. Add to that the addition of a filter through the use of goggles or a lens attachment and you can improve the contrast even more.

Sometimes, the glare from the background can produce undesirable effects. To reduce this problem, use a Styrofoam coffee cup with the end cut off to diffuse the light. This technique is covered in a previous post about the use of Amido Black.

Once you find the best angle and combination of light and filters, you will need to photograph the fingerprint. Place a scale on the same plane as the fingerprint and set up a camera on a tripod perpendicular to the surface of the print. Turning off any ambient light in the room will help tremendously.

After a while, you will be able to recognize this type of print before you ever try to apply powder or Cyanoacrylate. In any case, all evidence should be examined visually and with an alternate light source (when available) prior to the application of anything.

Camera Settings

2008-02-20T22:18:00.007-05:00

I’ve been reviewing the keywords that have been used when people find this website and noticed that there are some questions that are presented in these keywords that have not been answered previously. I thought it would be a good idea to pick one from time to time and explain the answer.

Keyword Search: “Best F-Stop Setting for Taking Footwear Impressions”

For those who don’t know, there are three main considerations when adjusting your camera’s settings for each photograph. They are the shutter speed, f-stop, and the ISO.

Shutter speed is measured in either seconds or fractions of a second. Anything longer than 1/60th of a second needs to be mounted on a tripod to prevent blurring of the photograph due to camera movement. 1/120th of a second is preferred for freehand photography. Faster shutter speeds will make it possible to photograph moving items with clarity, although this is rarely a consideration for crime scene photography.
F-stop is a setting for the aperture, or how far the shutter will open. The larger the f-stop number, the smaller the aperture. This causes some confusion for new photographers, but becomes second nature fairly quickly. Aperture determines the photograph’s depth of field. A shallow depth of field is ideal for portrait photography where you want the model’s face to be in sharp focus, but the background to be blurred thereby focusing the viewer’s eyes on the subject. A low f-stop (f2.8) will create this effect. This effect becomes amplified as the subject moves closer to the lens. For crime scene photography, this causes a problem when taking certain photos. A fingerprint on a curved surface needs to have a greater depth of field so that all portions of the fingerprint are in sharp focus. For this reason, a higher f-stop (f32) should be utilized. The same is true for photographing footwear or tire impressions.
The ISO determines the camera’s sensitivity to light. On 35mm cameras, this is equivalent to the film speed. A lower number (100) means less sensitivity to light. A higher number (3200) means a greater sensitivity to light. Generally speaking, a lower ISO produces a photograph with finer detail although this is not always true. With today’s high-end digital cameras, the ISO is used primarily to help achieve the desired shutter speed and f-stop.

The trick to determining these three settings is to understand how they all work collectively rather than independently. It’s all about getting a sufficient amount of light to the sensor or film inside of the camera. When the aperture is small, less light reaches the sensor. This can be compensated for by increasing the shutter speed or ISO. Likewise, a larger aperture might allow too much light into the camera which would require a decrease in the shutter speed or ISO. Changing one setting affects the others.

I prefer to determine which setting is the most critical for each photograph and then adjust the others accordingly. When photographing evidence, the aperture is usually the critical component due to the desire for depth of field. Many cameras in use today have a number of composite settings that make this task fairly simple. Most people use the “P” (program) setting which adjusts the big three automatically. Some use the “M” (manual) setting where the user has to set each of the big three manually. But there are also “S” (shutter speed priority) and “A” (aperture priority) settings which allow the user to set one and allow the camera to determine the other two to produce the preferred balance.

So, to answer the question presented by the keyword string…
- Use the highest f-stop possible with the available lighting.

Remember to place the camera on a tripod perpendicular to the surface of the impression and place a scale next to the impression. Use a remote shutter release to avoid shaking the camera or moving the tripod. Take an initial photograph with available lighting. Then take four more photographs using a handheld flash unit. For these photographs, hold the flash on one side of the impression at an oblique angle so that the light casts shadows in the impression. Do this for each of the four sides of the impression. This will give the examiner detailed information of the entire 3-dimensional surface. After you’ve completed the photographs, you’re ready to make a cast of the impression.

3-Dimensional Representations - The Sequel

2007-10-16T19:55:00.001-04:00

I had written a less than flattering post about Vista FX3 back in February. I still refuse to give up on the software and try to make it work from time to time time. I added the extra time on that last sentence because what I'm really doing is wasting time. I need to just wait for an updated version and see if it has improved enough to be worthwhile.

On the other hand, I have discovered a new program that is more flexible and easier to use. Google SketchUp which is absolutely free. It has the same basic design features as Vista FX without all of the bugs. You can create buildings and place walls, doors and windows with the click of a mouse. Everything can be done using measurements right down to the thickness of the walls and the height of the windows. There is even a measuring tape tool that allows you to add the measurement markers simply by drawing a line. The first time I tried it, I created a two story residence with furniture and an intricate roof in approximately one hour. Users can also create and share their models in the 3D Warehouse so you can usually start with a model that's already close to what you need and just tweak it a little.

I immediately began comparing Google SketchUp to Vista FX3 and determined that the similarities are astounding and the differences are gratifying. SketchUp has all of the "fancy" abilities as Vista; photogrammetry, photo overlay, and scaled 3-D modeling. What it doesn't have is a difficult interface, an overwhelming drain on the CPU, and a fistful of bugs. The only point that Vista has in it's favor is the ability to animate a scene....wait a minute! So does SketchUp! You can set up a walk-through of your model and export it as an .avi, but you can't animate individual objects the way you can with Vista. I consider object animation to be a bad idea anyway since there is so much interpretation required.

In my opinion, SketchUp is what Vista wanted to be. It has all of the important features and then some. Let me boil the comparison down to one specific example. Vista will allow you to create a rectangular building with ease as long as it has a flat roof. My instructor told me that there was a way to create a peak, but he hadn't figured it out yet. After months of trying, I haven't either. With SketchUp, I created a mult-winged building with a multi-faceted roof in less than five minutes. Isn't that the point of 3-D modeling software for crime scene investigators? If you want to play around even more, you can place your model in Google Earth and view it with all of the terrain already built in!

I'm not ready to stop using Adobe Illustrator for crime scene sketches, but for 3-Dimensional crime scene representations, Google SketchUp is everything you need - for free. If you are proficient with CAD software, you might want to go Pro for $495, but the basic version is more than enough for crime scene investigation.

By the way, I'll probably get sued by Visual Statement for bashing their program, but they don't deliver what they promise and everyone should be aware of the problems before throwing good money into a bad deal.

On or off?

2007-10-02T11:22:00.000-04:00

Occasionally, a valuable piece of information during a crime scene investigation is whether or not a light was on at the time of the incident. This is commonly required during traffic accident investigations. For instance, one vehicle collides with the rear of another vehicle at night. The driver of the rear vehicle states that the taillights of the vehicle in front weren’t working. Another scenario is when a vehicle pulls out in front of another vehicle at night and the driver claims that the other vehicle did not have its headlights on.

There is a way to tell if the lights were on or not without having to depend on the statements of people who may be trying to hide their own fault. It involves examining the filaments under magnification. It doesn’t require a lot of magnification and can usually be done with a camera alone, depending on the lenses available for that camera. I prefer to use a macro lens which allows for very detailed close-up photography. But first, it helps to understand how light bulbs work. Very simply stated, a light bulb is a wire encased in a glass container that is filled with a gas. As electricity is passed through the wire, the wire becomes hot and glows. The gas is used to remove oxygen and prevents the filament from burning up. Most modern lights use coiled wire. When a light bulb is impacted while it is illuminated, the filament is malleable and will bend. If the light bulb is impacted while it is not illuminated, it is inflexible and will break if the impact is strong enough. It’s a lot like plastic in that when force is applied to cold plastic, it breaks. If force is applied to hot plastic, it bends.

This photograph is from a headlight that has two settings: low beam and high beam. Notice that there is a separate filament for each setting. On an undamaged bulb, both of these filaments should be straight and shiny. In this case, one of the filaments is a straight coil while the other is bent. This bulb is from the headlight assembly of a vehicle that struck another vehicle. If you’ve ever been involved in an accident, you know that your body keeps moving in the direction you were going (inertia) while the car is stopping suddenly from the impact. It feels like you are being thrown forward in your seat. The force that you feel has the same effect on every piece of the vehicle including the headlight filaments. One of the filaments was hot enough to bend, the other wasn’t.

This photograph is from the other headlight on the same car. Notice that the filaments are similar to the last photo in that one is bent and one is not. But in this photograph, the bent filament is discolored. This is caused by oxidation. If the glass on a light bulb breaks during the impact, an illuminated filament will essentially combust when it contacts the oxygen in the air causing the wire to become oxidized making it appear discolored or even burned. If the filament is not illuminated when the glass breaks, nothing happens. The discoloration on the bent filament is a result of the tip of the glass breaking just enough to allow the gas to escape which let oxygen in. In some cases, you will even be able to see small round spots on the filament where tiny fragments of the glass landed on the filament while it was still hot causing the glass to melt to it.

As always, interpretation of the evidence should be done by an expert. There are certain cases where it can be tricky. For instance, what if the light had been on for some time but then turned off shortly before the accident? The filament will still be hot enough to bend even though the light was not on at the time of the impact. There are several factors that need to be collectively considered before making a final conclusion.

Powder and water aren't always enemies

2007-05-03T11:13:00.000-04:00

As a part of ongoing training in crime scene investigation, our Lab has developed a training and familiarization exercise that is conducted every week. It consists entirely of trying to find items that seem unlikely for processing and then finding ways to process them. By doing this, we learn first-hand what process works best for specific items and figure out ways to collect evidence from things that most other people wouldn’t even try. Recently, we experimented with some plastic bubble wrap that had been lying on a shelf in the work bay for months.

Several methods were attempted consisting of basic powder, magnetic powder, fluorescent powder, iodine fuming, ninhydrin, cyanoacrylate and dye stains. We even played with Liquinox and gentian violet. Nothing worked very well but the most promising method seemed to be magnetic powder. We could see some ridge detail but most of it was obscured because the powder was also sticking to the background behind the print. These photographs were taken with rear illumination using a light box.

Inv. Nancy Peacock decided to try a few things that weren’t in the standard arsenal of crime scene processing. Since mag powder performed slightly better than the other methods, she modified the application. After fuming a piece of bubble wrap with cyanoacrylate, she applied magnetic powder. But then she rinsed off the plastic with plain water. What she discovered was that the background scatter rinsed off and the latent print still remained. The clarification of the print was astounding. She tried a few more experiments and made a slight improvement to the rinse by adding Photo-Flo.

One important point I would like to add to this technique is to be careful of reverse prints. We have repeated this experiment several times on different items and have found that the prints will be reversed in some cases but not in others. We are still trying to identify the exact properties of this method to determine why it is not consistent in regards to print reversal. The print on the left is a reversed print which is indicated by the lighter color of the ridges over the background color rather than darker color ridges over the background.

The next time you use mag powder and end up with a tremendous black mess, you might want to give this idea a try. More than likely, you will end up with a viable print. If that doesn’t work, try something that no one has ever suggested to you before. You might just end up with a new technique that you will find yourself using for the rest of your career.

Choosing the right weapon...

2007-04-20T20:36:00.000-04:00

The most important and oft-used item in a crime scene investigator’s inventory is the camera. In a market that is saturated with hundreds of choices, how do you find a camera that is best suited to your purpose? The search becomes a lot easier if you know the specifics of what you’re looking for.

Begin with the type of camera. Do you want digital or 35mm? Most agencies have made the switch to digital for several reasons. You don’t have to pay for film and film development which costs more over time than the camera itself. You can see the photographs immediately which is incredibly helpful when using difficult photography techniques like Painting with Light or Alternate Light Sources. You also don’t have to constantly swap out rolls of film on larger scenes. There is only one drawback with digital cameras and that is storage of your photos. They can easily be stored on CD but there is some concern over the archive capability of CDs. The main concern is how long will CDs last and how long until they become obsolete. You may be forced to transfer all of your stored photographs to a different media several years from now as technology advances. In my opinion, it won’t be long until 35mm film is obsolete and, unless you have your own photo lab, you won’t be able to print the pictures. So let’s discuss digital camera options.

Almost everyone is obsessed with mega pixels. It’s not necessary. Once you get to a certain point, there is no need to go any higher. Higher is better, but not necessary. A 6 mega pixel camera is capable of taking high quality photographs that rival 35mm. Let’s move on to more important considerations.

Crime scene investigation requires flexible photography options which means that the lens is as important as the camera. Digital cameras have what it known as a ‘crop factor’ which means that a 28mm lens will act like a 35mm lens when used on a digital camera. The photograph on the right was taken with a 35mm camera using a 50mm lens. The white box represents the photography area of the same lens on a digital camera body. I prefer to carry 3 lenses. The primary lens is an 18mm-120mm zoom lens. By having a lower range of 18mm, my lens is capable of photographing a large portion of a room in one shot. There is a very slight fish-eye effect at 18mm so don’t use that setting for photographing where scale is important. By having an upper range of 120mm, I can stand in one area and take several shots while zooming in to give reference points to important items. It’s a very good overall lens. I also have a macro lens for close up photography which I use for tool marks and latent prints. The third lens is a 70mm-300mm telephoto which I use when doing surveillance or taking aerial photographs. Because of the lens requirements, you should look for a camera body that has a removable lens. If you already have a collection of lenses, make sure the camera body is compatible with those lenses. Just remember the crop factor. You might end up needing a wider angle lens with your new camera.

Another area to consider is the flash. I like having a built-in pop-up flash on my camera just to have as an extra option, but you really need to make sure that the camera also has a hot-shoe for attaching external flashes. There are several conditions that will require you to take the flash off of the camera and hold it off to the side, like when photographing footwear or tire impressions. You can’t do that with a built-in or straight-on flash.

A minor point to consider is what kind of storage media does the camera use. There are several types out there which can make it difficult to decide. Look at the different types of media like Compact Flash, Smart Media, Secure Digital, Micro-drive, XD, Memory Stick, etc. and compare the cost of each and the available capacities. I prefer to use 512MB cards over larger ones. Because of the lower cost, I can buy more for the same money but I can use a different card for each scene if I don’t have a chance to download the pictures between scenes. Plus, 512 is usually more than enough to capture an entire scene. Compact Flash is small enough in size to store yet big enough to handle with ease, unlike XD cards which are so small that they are very difficult to manipulate. They are also very sturdy and can take a lot of abuse unlike Micro-drives which having moving interior parts and are not very shock resistant. Many professional cameras have the ability of using more than one type of storage media which adds flexibility.

Finally, look at the camera’s available settings. Try to find one that has the option to switch between Automatic/Program (P), Shutter-speed Priority (S), Aperture Priority (A), and Manual (M). Most of the time, you can use the Program setting to have the camera adjust each shot automatically for the lighting conditions. You will also need to have the Manual option for advanced techniques, primarily, Painting with Light. Another important consideration is the availability of a Bulb setting which means that the shutter will stay open as long as the button is pressed. You’d be surprised how many professional cameras have a maximum exposure of 30 seconds with no Bulb setting. Also, look for a camera that is capable of using a mechanical remote shutter release cable rather than electronic. Mechanical remotes are usually less than $10 but electronic remotes can top $80 easily.

Once you find a camera that meets all of your needs, don’t stop there. Learn everything there is to know about that camera. Some of them are quite daunting and navigating the menus can be a very in-depth venture, but the more you know about your camera, the more comfortable you will be using it. Learning the camera is also important when little things go wrong and require a little attention. For instance, getting the F-ee error can be caused by something as simple as the F-stop being improperly set on the lens and can be corrected by rotating the F-stop ring to the proper setting. There are also a lot of little things built in to the cameras, like white balance, that can help you if you know about them and hurt you if you don’t.

Fingerprints from what???!

2007-03-28T17:00:00.000-04:00

Sometimes, you run across items that you know were in the suspect’s hands that don’t lend themselves to traditional fingerprint processing techniques. Even with all of the possibilities like powder, ninhydrin, amido black, small particle reagent, Liquinox…just to name a few…there are still a few items that seem impossible. In case you can’t think of any, let me throw this one at you…

Cabbage.

Fingerprint powder, even magnetic powder, sticks pretty evenly across the leaves and doesn’t enhance the latent prints. Ninhydrin turns the entire thing purple and wilts it almost instantly if you use an acetone base which changes the dimensions of the print. Amido black will only work if the print is bloody, and the glacial acetic acid/methanol combination isn’t friendly to vegetation. Small particle reagent sucks in general, but has the same problem on cabbage as powder. Liquinox and similar processes only work on skin cells embedded in glue.

Why would you want to process a cabbage? The same reason as processing anything else – because it may have the suspect’s prints that could identify the perpetrator. As a specific example, I worked a vandalism at a fruit and vegetable packing center, which usually doesn’t warrant a crime lab response, but there was nearly a quarter of a million dollars in damages to the forklifts and other heavy equipment that the suspects drove off of the end of the loading dock. I tried to get fingerprints from the machines, but they were too caked with oil and grime to get anything worthwhile. The suspects had thrown around a lot of fruit and vegetables, but most exploded on impact, like tomatoes. The only thing I had left to work with was cabbage. There were about a half a dozen heads of cabbage laying on the floor that the suspects had thrown, but didn't disintegrate like the other produce.

The solution is an often overlooked process – cyanoacrylate dye. Fume the item with superglue as you normally would and let it sit for a day to allow the superglue to set. Then either spray or dunk the item in a fluorescent dye stain. I prefer to use RAM which is a combination of Rhodamine, Ardrox, and MBD. Allow the dye to remain on the surface for about 30 seconds or so and then rinse it gently with distilled water. Using an alternate light source in a dark room, examine the item for latent prints. They will glow brightly and can easily be photographed with a scale for identification. I have used this technique successfully several times when nothing else seemed to work. It also was the key to solving a major crime at the packing center.

3-Dimensional Representations

2007-02-28T20:26:00.000-05:00

Throughout the years there have been many methods of sketching crime scenes. When I started, I used graph paper and a pencil. I eventually started using Adobe Illustrator which is great for doing scaled diagrams, but is not exactly user-friendly. I have tried other programs on the market that are capable of creating 3-Dimensional representations, but have never been impressed. The graphics are very poor and I would be embarrassed to try to pass it off to a jury.

My department recently acquired Vista FX3 which was designed by Visual Statement. The first versions of this software were geared toward traffic accident reconstruction. Over the years, Vista FX developed into a very capable program. Visual Statement recently added a crime scene module to their software. I spent five days in training to learn how to use this software effectively.

The catch is, you can’t use the software effectively. While it may be useful for traffic accident diagrams, the crime scene module of Vista FX3 is exceedingly flawed. Several times during the training, the instructor would have us create 3D representations of specific scenes, like a person jumping off of a building, for instance. We spent nearly an hour setting up a simple non-detailed scene including only a skyscraper and a person jumping from the roof only to watch the person disappear from the screen each time the animation started. Another hour later, we were all seeing red as the instructor tried to convince us that we were all doing it incorrectly and we were all morons. Eventually, he admitted that it must be a bug in the software. I didn’t mind that so much because the chances that I will ever have to animate a person jumping from a skyscraper are practically zilch. What I did mind is that bugs were so predominant that the instructor asked me to spend a day of the training trying to find a way to create a building with more than one floor where you could place the scene inside of the building. It is nearly impossible, but it can be done. Because of that little adventure, I missed out on a full day of training just to show the company how to fix their own software.

VistaFX3 actually has great potential (which is why my department purchased it) which includes “smart” designs where you place one section of a building near another, and they automatically ‘snap’ together seamlessly. The graphics are impressive as long as you use them on a fairly beefy computer. You can also add crime scene photographs on top of objects, including floors and walls, in the diagram to make them look incredibly realistic. And the examples they use to sell the product show incredibly detailed scenes with animated figures, blood spatter, bullet trajectories, blah, blah, and blah. Of course, few of these examples could be successfully recreated and must have taken the designers months to build.

As I sat through this mire of technology, I started to wonder how much use I would get out of it. I have never had a problem on the stand explaining the chain of events using photographs and physical evidence. The jury always got it and my testimony has never been successfully challenged. On the other hand, if I start bringing 3-D animations into the courtroom, the door is opened for intense scrutiny. With photographs, I can prove what happened. With evidence, I can prove who did it. But there are a lot of unknowns in between. For instance, was the shooters left arm at his side during the murder? – or was it in some other position? Did the victim have their arms over their face when they were shot in the chest? – or were they reaching out toward their attacker? These are points that have no relevance to the fact that the suspect murdered the victim, but have to be interpreted in the animation in some way. So now the defense attorney starts questioning these things. Should I tell them that this is only my artistic interpretation? – or that it’s none of their business?

I usually embrace technology. The exception is useless technology. This program definitely comes under the heading of useless. If you are looking for ways to spend your department’s money, spend it on better cameras, light sources, or graph paper. I would consider a truckload of Frisbees to be a better purchase.

Don't Sweat the Small Stuff

2007-01-22T13:34:00.000-05:00

Occasionally during an investigation, it becomes necessary to find a needle in a haystack. Other times you may be required to find a toothpick in a stack of needles. If I'm not making any sense, climb aboard the band wagon and allow me to explain.

There are times when you have to sift through a large amount of dirt or debris in order to find small articles of evidence like shell casings, projectiles, or even teeth. I use a homemade screen made out of 2x4s and wire mesh. It's big enough to require two people (one on each end) to shake it back and forth until all of the debris falls through and I'm left to manually sort through the remainder to find what I'm looking for. It's not so bad when dealing with dirt, but it can be a pain in the neck when dealing with fire debris.

The problem with fire debris is that it almost always has a large amount of fiberglass insulation and it's always wet from the fire hoses. When you try to shake it through a sifter, the fiberglass makes the debris clump up into balls that won't go through the screen. If you try to use your hands to rub the debris through the screen, you'll shred your hands on all of the broken glass and wire and other sharp little nasties.

I found a solution that solves this problem. More water. Prop up at least one end of the sifter with whatever you can find. Place the debris into the sifter and use a garden hose to wash the debris through the screen. Not only does it remove all of the debris that will fit through the mesh, but it also cleans off everything that's left making evidence much more visible. It works well with fire debris, but works incredibly well with dirt.

The next time you need to sift through a large amount of dirt or debris and happen to have access to a water source, give this a try. You'll be surprised by how well this technique can work.

Preparing for Court

2006-10-15T21:28:00.000-04:00

Having worked in Crime Scene Investigation for many years, I have also had my fair share of experience testifying for major trials. One of the most important things I have learned over the years is to tie up the loose ends. It's easy to do and easier to forget.

When I start working on a major case, especially a 'whodunnit', the only thing I want to do is to find that one piece of evidence that identifies the suspect. A bloody fingerprint, a smattering of DNA...whatever. While I'm looking for that Holy Grail of Crime Scene Investigation, I collect an awful lot of other stuff along the way. A tire casting, a hair fiber, or even a bunch of latent fingerprints. If I get lucky enough to find a piece of magic that links me to the bad guy and solves the case, I almost always have to take a break and catch my breath. Especially if I've been working for several days and nights with no sleep.

The problem comes when you have to start working on another case before you tie up all of the loose ends on the one before it. Sure, we caught the guy, but we still have to win that case in court. That means you need to take all that extra stuff that doesn't seem to matter anymore and analyze it anyway. The last thing you want to happen in the middle of a trial is for a defense attorney to bring out all of this evidence and ask you what you did with it. "Did you really have all of this evidence that could have proven the innocence of my client and you didn't bother to even look at it?" It doesn't matter how 'airtight' your case is. When it goes to a jury, it's what the layman believes. If he thinks you did a poor job, your airtight evidence goes out the window. However, if you can tell that defense attorney about all the tests you did on all that other stuff even though you had solved the case, then you'll look good in the jury's eyes and they'll be more apt to believe you.

After all, we don't have to convince ourselves, the prosecuting attorney, or even the judge. It's all up to those twelve people that sit in those chairs across from you that make the ultimate decision.

Evidence Management

2006-06-24T22:23:00.000-04:00

I wanted to talk about an often neglected area of Crime Scene Investigation and that is Evidence Management. My department currently has over 16,000 items of active evidence. As with most agencies, money is short and methods of keeping accurate records of evidence are hard to obtain.

Until 2001, I suffered through years of using an ancient program called dBase III which is a DOS based system. It crashed in 2000 because it was not Y2K compliant. We patched it up the best we could and trudged on. I tried to get new management software, but the expense of these programs turned this idea into wishful thinking. What I didn't realize is that I had an effective tool the entire time.

Most departments have computers. Many of these computers are equipped with Microsoft Office. If you fall into this category, check to see if you have Microsoft Access. If you do, you have a real possibility of creating a highly effective and powerful Evidence Management System. It may be challenging if you don't know how to use Access, but if you are looking for a solution, it will be worth your while to learn. Access is a database program. It can store as many columns of information as you need and can use multiple tables. You can search this information any way you want which is essential. It is able to import data from many different sources, so chances are you can pull over all of the information from your current system. It also has a tool called a Switchboard Manager which allows you to create custom menus to make it easy for people to use even if they don't like computers. The part that I really like is that you can create a multi-user environment so that several people can add and edit evidence information simultaneously. With dBase, we were stuck with one computer and only one person could work on it at a time. Now, when I have large amounts of evidence come in at once, I can have several people knocking it out all at once. I have also incorporated Barcoding which is quick, easy, and accurate.

The end result is a polished, professional, and powerful Evidence Management System. It is expandable and, best of all, it can be customized by the people who use it without having to call in a team of 'experts' to tell you what you need.
And you probably already have the software that you need - if not, Microsoft Access can be purchased at a much lower cost than what specialized companies try to sell their products for.

If you are thinking about taking on a project like this, please contact me. I will be happy to tell you about the pros and cons as well as give you advice on how this could work for you.

Night Photography

2006-04-21T10:18:00.000-04:00

I was reading an article in my favorite magazine the other day and was rather disturbed to find an article of the 'how-to' variety teaching ineffective crime scene techniques. The article covered night photography and different methods you can use to take pictures in low-light situations. I'll admit that capturing images at night can be tricky, but the methods taught in this article were just wrong. The author explains how to use emergency lights, spotlights, and street lights to illuminate the scene. There are even photographs that show these techniques at work. The problem with the photographs is that they are all mid to close range photos that you can take easily with an on-board flash. Only one photograph is an overall scene picture which only came out because of ambient lighting (which means you could have put the camera on 'automatic' and gotten the picture). All of the emergency lights, spotlights, and street lights are actually harming the photographer's efforts.

When a regular flash won't work, you do have options. You can take a crappy picture like what was in the magazine. You can put the camera on a tripod, set the exposure levels to automatic, and use a shutter release cable. (A little information on automatic metering....There is nothing wrong with it! It is actually more accurate than any other type of metering provided you use it correctly.) Or you can do it the right way - you can "Paint with Light".

Painting with light takes practice - preferably before you need it at a scene. It also requires a fairly decent camera which most Crime Scene Units should have. It also requires a separate flash unit which, again, most Crime Scene Units should have. Place the camera on a tripod, set the shutter speed to 'bulb', and attach a shutter release cable. Disable the autofocus and on-board flash. Set up the camera and set the focus. Get the scene as dark as possible and lock open the shutter. With your flash unit in hand, walk to the far end of the scene and start flashing as you walk back toward the camera. Three quick tips:

1) Hold the flash at a slight upward angle to avoid hotspots on the ground,
2) Avoid pointing the flash back toward the camera,
3) Wherever you stood for the first flash should be where you aim the second flash. Wherever you stood for the second flash should be where you aim the third...and so on.

These photos were taken by a co-worker during practice. The first uses just the on-board flash. The second was painted with light and actually could have been done a lot better, but that's why we practice. They are, however, much better than what was shown in the article and can be done by anyone who is willing to put a little effort into their work and not look for shortcuts. It works with 35mm and digital, although you can see the immediate result with digital.

With a Little Help From My Friends...

2006-04-18T12:16:00.000-04:00

Whenever we hold interviews for a new Crime Scene Investigator, I'm always interested in how well the candidates can think outside the box. We all get a lot of training in how to handle most circumstances, but what about the rest of the circumstances? A good investigator can tell you the best way to apply the training but a great investigator can find a way to do something for which there has been no training. Some things in this line of work are just so freakish that you have to create your own method to get the job done. The first thing I try to do in this situation is to find someone else who has done something similar, but for a completely different purpose. For instance...

My agency recently got new information on an old homicide that was never solved and the murder weapon had never been recovered. (I must be vague about the details since it has not gone to trial yet). The information proved to be accurate and we made several arrests. We also recovered the weapon. The problem is, it had been laying in a marsh for years and was severely corroded. As I photographed it, my mind raced back to episodes of Jacques Cousteau and how ancient metal disintegrates as soon as you remove it from salt water. I had never been trained for this specific instance nor had anyone in my office or surrounding agencies. As usual, I made it up as I went along. I 'borrowed' my friend's plastic tote box and filled it with water from the marsh and then placed the item in the water.

After getting it back to my office, I realized I needed help. I wondered who would know anything about processing metal objects that had been in salt water for years. The scientists who are working on the Hunley do exactly that kind of thing but with a different purpose. It sounded like a good place to start so I looked them up on the internet, sent them an e-mail, and got a response back in less than 8 hours. They have been assisting me with this project ever since and have also put me in touch with other experts who have volunteered their time. As it turns out, not only have I found a way to preserve the evidence from this homicide, but I stand a very good chance of recovering trace evidence from the weapon that can give me that final little piece of evidence that makes this a slam-dunk case.

Thank you to all of my friends on the Hunley project - or Team Hunley as I call them. I would like to thank them individually, but several of them have asked to not be named - they prefer to stick to the science rather than the publicity.

Duct Tape

2006-03-21T13:11:00.000-05:00

Many people know the benefit of collecting fingerprints from duct tape. By using either the sticky-side method or the Liquinox method (I prefer Liquinox) you can develop some outstanding ridge detail on the glue side of the tape. It works exceptionally well in a laboratory environment, but not so well in the real world. The biggest problem comes from trying to unravel the duct tape from whatever disformed shape it was in when you recovered it. I have tried several possible solutions to this problem including an oily substance specifically designed for this purpose (which dissolves the glue and the print). Only one method works reliably and that is... refrigeration.

I prefer to place the tape in a refrigerator for several hours before trying to unravel it. In severely sticky cases, you might have to place the tape in a freezer instead of a refrigerator. If you do not have access to a refrigerator or freezer, you can use liquid nitrogen, but it isn't very practical and it's not readily available. However, there is a portable method that can be purchased at any electronics or home-improvement store. Canned Air. If you hold the can upside down while spraying, it emits an incredibly cold mist that will freeze anything in its path. Cover the duct tape with this mist and let it sit for a few minutes - it is almost as good as placing it in a freezer. Please be extra careful if you use this method! The mist will absolutely freeze anything in its path - especially human skin! It will cause a very painful injury that takes an enormous amount of time to heal and will cause severe scarring. That having been said, it works great on duct tape.

Amido Photography

2006-02-27T19:38:00.000-05:00

A few years ago, I was working on a homicide and as many death scenes dictate, I ended up using Amido Black to try to get the suspect's fingerprints in blood. The scene occurred in a car and I dismantled the entire vehicle and processed each individual part. When I was working on the rear view mirror, there were bloody smudges on the glass portion, but there was no blood visible on the back side. After going through all of the prerequisite steps, I sprayed the back of the mirror with Amido and instantly saw ridge detail covering the plastic. Unfortunately, as soon as it dried (which was almost instantaneously) I could no longer see the ridge detail and every attempt to bring it back up was fruitless. After weeks of trying every weird thing I could think of, I found a solution.

STYROFOAM COFFEE CUPS!

Cut the bottom off of a styrofoam cup and place the mouth of the cup over the object. Use an alternate light source through the side of the cup to illuminate the object. The styrofoam cup acts as a universal light diffuser. Place an appropriate filter over the bottom of the cup and photgraph the object through the hole. It takes several hands to get it, but when you get the light at just the right angle on the surface of the object, you will be able to see the developed Amido print on some unbelievable surfaces.

If you've ever had this problem, give this a try. You'll be surprised.

Silicone Casting

2006-02-21T14:21:00.000-05:00

I discovered a product that replaces Mikrosil, Rough-Lift glue, and gelatin lifters. It is called AccuTrans® and it is made by Ultronics®. It is a silcone-based casting material that is similar to Mikrosil, but comes in a gun and cartridge system. NO MORE MIXING! Imagine putting Mikrosil in a caulk gun - it's that easy. It comes in brown for toolmarks, and white for fingerprints. The big news is that it also comes in clear! This allows you to use it to lift fingerprints but without having to work with a reverse lift! This replaces Rough-Lift glue and gelatin lifters! All three colors will set in about five minutes. I'm not trying to sell the stuff, I just want to let everyone know it's out there. I initially read an article about it in Evidence Technology Magazine which was interesting enough for me to contact the company. The sent me a sample of brown and clear to try out before I bought it. And if you really like hand mixing from tubes, they sell it in tubes as well. There is a very detailed article available online from Forensic Magazine if you're interested.

And so it begins...

2006-02-21T13:42:00.000-05:00

In an era when technology has overrun itself and we find ourselves immersed in a world of gadgets that claim to perform remarkable feats, I propose we band together and share our knowledge and learn from successes as well as failures.

I have been working for a sheriff's department in a major city for 19 years, 10 of those years have been in crime scene investigation. My motto is "I'm not young enough to know everything". This forum will be for those investigators who have tried everything they can think of and are willing to try something that someone else has thought of!

I would also like to encourage everyone to share new discoveries of what works and what doesn't before it becomes a necessity.