Monthly Archives: February 2012
Taser AFID Tags
The Taser has become an invaluable tool in law enforcement; as prevalent as handcuffs and a side-arm on the patrolman’s duty belt. The less lethal control device has undoubtedly saved lives and prevented the kinds of injuries sustained by combative subjects in decades past. When the officer shoots the Taser two probes are launched from the cartridge and once embedded under the skin will temporarily incapacitate the subject by introducing a pulsed current.
Anti-felon Identification Tags (AFIDs) are small serialized confetti-like discs packed into each taser cartridge (the piece that houses the probes that are launched toward the subject). Each cartridge contains between 20 and 40 tags and the alphanumeric serial number on each tags corresponds to the serialized cartridge issued to the officer. In normal light the tabs are colored pink, yellow, and even translucent. But the tags have another useful feature; they are visible under ultra-violet light making them easy for CSIs to find at the shooting scene. AFID tags were introduced to provide some accountability of which Taser was fired in which relative position at a shooting scene. In some ways this evidence is similar to an analysis of fired cartridge cases. A recent study indicated that 75% of these tabs will be found within a 120 sq. ft. area in the direction of fire. That may seem like a large area but it is basically 12 feet in front of the shooter and about 5 feet on either side of the center-shooting line. Having said that, there is no defined “pattern” of distribution as this can be affected by many of the same conditions affecting expended cartridge cases.
AFID Tags in Normal Light
AFID Tags Under Ultra-violet Light
So how are these tags used in an investigation? First, they help confirm the relative position of the deployed Taser. If officer X says he was taking cover behind a door and fired from that position we should find AFID tags in that general area. If the tags are from another officer’s Taser then the officers have to explain that. In high stress scenarios some officers can’t remember exactly where they were when they deployed a Taser, especially if additional use of force methods (such as shooting), chasing, or extensive searching occurs. They also help to show how many officers fired their Tasers at a given scene. These tags are durable and can be found days and weeks after deployment. Many agencies have a policy stating that officers are required to collect the spent cartridge and a sample of the tabs at the crime scene.
So how can you use this information in a novel? Well, most criminals probably don’t know about these tags. Imagine a scenario in which an officer’s Taser is stolen. Days later it is used to commit a crime and the suspect unwittingly leaves behind these tags. The CSIs investigating the scene are now able to link the two crimes together which may provide a clue as to the suspect’s identity. It could be any number of people who could have had access to the officer’s Taser or they may have lost it in a scuffle. Use your imagination and consider an unusual suspect.
The Amido Black Blood Reagent
There are a number of other blood reagents like Luminol, Fluorescein, and Leucocrystal Violet that seem to be much more commonly referred to in literature and on television but Amido Black is another one you might consider using in your story. Amido Black is a presumptive blood reagent (can’t discriminate between human and non-human blood) that is very useful in developing diluted or latent blood impressions like shoe prints. This makes it an effective tool in the bloodstain pattern analysts arsenal. Amido Black is a water or methanol based dye stain that reacts with the proteins in blood turning them a dark blue-black color). The process begins by “fixing” the possible blood impressions with a methanol wash prior to the application of the reagent. Sometimes this methanol is mixed directly with the reagent at the time of application. The solution can then be sprayed or poured over the testing area. Some smaller items of evidence can be “dipped” in trays of the reagent as well. The reaction may not be as “flashy” as one of the luminescent reagents but it can be just as effective.
The sensitivity of the reagent is thought to be about 1:10,000 (parts per blood dilution) and has no detrimental effects on subsequent DNA testing although if too much reagent is “washed” over the evidence the sample could become too diluted for DNA testing. It can be used to detect any latent mark (such as tire print, shoe print, fingerprint, or tool mark) in blood at the crime scene. Once the reagent is applied and the blood impression is developed then the visible impression needs to be “fixed” with a 5% sulfosalicylic acid. The print can then be photographed.
I have successfully used this reagent many times at crime scenes and in the laboratory. It provides exceptional detail provided there is contrast with the background. That is the one potential problem with this reagent. Because it turns the blood a dark blue-black color, you can’t use it effectively on dark colored surfaces. That is something you’ll want to keep in mind if using this reagetn in your novel. The video below presents a homicide case in which Amido Black was successfully used to develop bloody shoe impressions from the suspect at the crime scene.
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The Scent of Fear is Now Available!
It’s been a very long road but I’m really excited to announce that my debut novel The Scent of Fear is now available!
Click here to order the e-book
Click here to order a Trade Paperback
I am so excited to share this novel with you. The concept of this story has been bouncing around in my head for the past decade but I never had the time to write it until I left law enforcement. It has taken a lot of twists and turns but I am thrilled with the result. I am already working on the next book in the trilogy and will keep you all posted on major developments at my new website.
Touring The Crime Lab: The Photography Lab
Photographic labs have undergone tremendous changes since the adoption of digital technology. For the edification of our historical writers I’ll try to paint a brief picture of the largely extinct film based labs. When I first began my career photography labs dealt with film. We used primarily 35mm color but occasionally dealt with Polaroid and Medium format cameras as well as specialty films like infra-red. Photographic film is, of course, sensitive to light. Controlled exposure to light (by proper apearature and shutter speed settings) is how a picture is imparted onto the film. That being the case, photographic laboratories contained a darkroom. A darkroom could range in size from a small closet to a 500 sq. ft. area but they all had one thing in common and that was the ability to be “light tight”. That means no windows and seals around doors to prevent “light leakage”. Some rooms even had neat revolving doors which were round spaces about 4 feet in diameter with a 2/3 sized opening which kept light from entering the darkroom as the technician entered the darkroom.
Revolving Darkroom Door
Developing film requires one to process the film through various chemical developers and washes (developer, bleach, fixative, wash). Prior to the 1960′s this was largely done with trays of chemical solutions. The photographer would take the film and dip it in each tray for a predetermined period of time until the image was developed and then hung to air dry. As police began taking more photographs it became necessary to automate this process. These machines contained tanks of the necessary chemicals and a conveyor belt like system to drag the filmstrip through the chemical at a predetermined speed (exposure). The rollers on these machines had to be cleaned everyday to keep the accumulated chemistry from building up and possibly scratching the negative. It was messy and smelly. One colleague actually worked in the FBI photo lab back in the Hoover days and was required to wear a 3-piece suit while working with these chemicals!
Wing Lynch Film Processor from the 1980's
Working in a darkroom takes skill. You would have to be able to break open the film container, attach the film to leader cards, and feed the cards in complete darkness. Some labs used red lights that in theory didn’t harm the film but most did not. Needless to say we used small tabs of glow in the dark tape to highlight tools and latches we had to find in the dark. I stubbed a lot of toes and banged a lot of knees. There would be one piece of equipment for processing film and another similar machine for printing the image onto paper. Each of these could be 4′ high x 2′ wide x 6′-8′ long. Later versions (C-41) could be used under normal lighted conditions with the invention of certain loading devices that could extract the film from the canister without exposing it to light. But starting in the mid to late 1990′s the digital wave took the industry by storm making these darkrooms largely unnecessary (although some labs still use a large printer for printing large numbers of digital images onto paper).
The modern police photo lab is pretty simple by comparison and doesn’t require nearly the same amount of real estate. Images are processed and stored on a computer instead of the old large processors. Again, in the old days you had to have huge file drawers or cabinets to store all those film negative strips. One piece of equipment that has survived the transition is the copy stand. The copy stand is a mounting system that allows the CSI to mount the camera on a perpendicular plane to the evidence being photographed. Most have adjustable arms with lights for oblique lighting as well.It’s very handy when doing close-up photography where you need a steady platform. It also frees up your hands to operate other equipment like an ALS.
A copy stand with "evidence" perpendicular to the camera image plane
Modern C-41 Film Processor
Another area that is commonly used is the “privacy room”. CSIs sometimes have to take pictures of sensitive areas (genitalia) from living victims. You can’t just ask them to drop their trousers in the main lobby right? You need a place that respects their privacy. That means no windows. Good photographers also like to use an industry standard 18% Grey colored background. This is the grey color you see in a lot of modern mugshots. The specific color allows photographers to calibrate the accuracy of the colors when printing. You can have the paint mixed to that color at any hardware store and simply paint the walls. It’s inexpensive and very effective. Some labs also use colored “curtains” or backdrops similar to what you might find in a commercial studio for the same effect.
Like any other room in the lab we still need plenty of drawers and cabinets to store the various lenses, filters, camera bodies, scales (rulers) and other nifty tools we use while photographing evidence and people. More sophisticated labs even have posable mannequins for use in displaying items of clothing or reconstructing body positions in reconstruction for court exhibits but that is a topic for another posting!
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Do Detectives Really Taste-test Drugs?
Remember all those great movie scenes where the detective dips his pinky finger into the bag of white powder and touches it to the tip of his tongue? Makes for dramatic television right? Do you think that’s actually what detectives do? For the real scoop on how drugs are field tested and why taste-testing is such a bad idea come check out my guest posting today on the Crime Fiction Collective here.
Ashes to Ashes: Do Arson Fires Really Destroy a Body?
This is a question I get from time to time so today I have a guest posting here to discuss the issue. A lot of people mistakenly believe that it is easy to completely destroy a body with fire; and while you can certainly do a lot of damage, destroying it completely is very difficult. It’s easy to think that fires are so destructive because we see what they can do to houses, forests, and the like but the truth is a bit more complex. If you have a scene like this in your novel stop on over at Stuff & Non-sense to take a look.
Searching for Trace Evidence Part 1: The Suspect
Trace evidence can be a very powerful tool establishing a link between a suspect and the victim or crime scene. In fact, the phrase “caught red-handed” refers to the guilt associated to a man having bloody hands. Bloody hands tend to prove that the suspect was in contact with the bloody victim (although technically may fall short of proving he committed the act). Bloodstained hands can be easily washed but trace evidence may persist for days, weeks, even years after the crime. CSI’s learn to search for trace evidence in areas the suspect may not consider and here are a few examples.
Spray paint on suspect's hands following tagging
Hair – The suspect’s hair may be a great reservoir of trace evidence, especially blood or fibers that may become entangled. Even if they wash their hands you may have several more hours before they wash their hair.
Nose & Ears – These are one of those locations that some CSIs forget about but nostrils and ears can trap important trace evidence like gunshot residue (GSR) or safe insulation. The nostril and ear canal contain hairs specifically designed to trap foreign particles and prevent them from entering the body so it makes sense that some types of trace evidence may become trapped as well.
Clothing & Jewelry - Trace evidence loves to get caught up in places like pockets, pant cuffs, and watch bands. Some evidence like soils, broken glass, or plant materials can also get wedged into shoe treads. Even if the suspect washes his clothing items like paint chips, seeds, and sand may be trapped in pockets and cuffs just waiting for a guy like me. Watchbands made of those flexible links may also hold trace amounts of blood not visible to a suspect. Remember, most men don’t clean their watch bands.
Suspect shoe with drywall dust from burglary scene
Vehicle – Suspects often take vehicles to their crimes and during their getaway may leave behind valuable evidence. This is especially true if the vehicle has dark interior colors (making evidence like blood harder to see). A suspect wearing bloodstained gloves may not realize he has left the victim’s blood on the steering wheel or door handle. He may also leave traces of blood or soil on the gas and brake pedals.
Residence – Suspects can even bring trace evidence all the way home. For example, a guy with muddy boots may kick them off in the garage breaking off chunks of the dirt onto the floor. Even if he picks them up and washes them there may still be dirt from the crime scene on the floor or swept under a cabinet.
So when you are developing your story think about what types of trace evidence you can use and how it might be “hidden” until the time your CSI finds it and blows the case wide open. Check back in a week or two for the next installment dealing with the crime scene.
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The Color of Fly Puparia
I’ve written before about maggots and how Forensic Entomologists use insect evidence in murder cases. Once maggots are done feeding on a body they will enter a pre-pupal or wandering phase and migrate to a safe place to pupate. The puparium is better known as a cocoon. It is the hardened cuticle (skin) that protects the pupa during its metamorphosis from a maggot to the adult winged fly. Maggots will spend approximately two-thirds of their immature life in this stage before emerging as an adult. During this time the puparium will go through several color changes.
Maggots are a milky white color prior to this stage so it makes sense that the initial pupal stage is a whitish-yellow color. As the maggot ages the cuticle will darken in color. After yellow, the casing will turn a reddish-rust color then brown. At first it might be a lighter brown and then darken to a deeper brown. At this point the adult fly will usually emerge by pushing through one end of the casing.
The pupal casing is extremely durable and can persist in the soil for thousands of years. Archaeologists have actually used ancient pupal casings to help identify the season of death at sites of bison kills and other dead animals in a similar way to a forensic examination. Fortunately, most murder investigations are much younger in age. The best way to use these color changes in your novel is through photography or personal observation by the detective.
Over the years I have had several cases where the pupal cases cold be seen in photographs but were not collected. Most of the time this is because detectives just didn’t recognize them as evidence. But if the cases are yellowish then I know they are at the beginning of their development. If they are dark brown to black they are much further along. It’s not exactly a precise measurement but it’s usually better than having just the maggots from the body. You may not even have photographs and instead have to rely on the visual observations of officers or detectives. Again, not ideal, but it’s usually better than nothing.
You can get pretty crazy with your descriptions or dialog. Detectives sometimes refer to these casings as rodent droppings. I’ve heard of cases where the detectives will actually take them to a wildlife biologist or scat expert in an attempt to determine what animal dropped them. I’ve often wondered how such an expert wold react if they were told the scene was littered with yellow droppings. It might take them a while to figure out that the evidence was from insects and not rodents! However you choose to use this information just remember that color changes can vary and aren’t as precise as other aging methods.
