Monthly Archives: May 2011
Superglue fuming is a chemical process to reveal and “fix” latent fingerprints on non-porous items such as bottles, firearms, knives, etc. The process work by heating liquid cyanoacrylate (i.e. superglue) which releases gaseous vapors that adhere to the oily residue of the fingerprint. In the laboratory this is done in a fuming chamber. When I first began my career this amounted to a fish tank. It was simple, crude, and messy. While I suppose some smaller agencies may still use these tanks the vast majority of modern labs use a chamber designed specifically for this function. These chambers control humidity and heat activation. Humidity is an important factor to control because the moisture in the chamber helps to re-hydrate the fingerprint residue. They also evacuate the dangerous fumes so the examiner isn’t exposed to them when they open the chamber up. With the old tanks we’d throw open the lid under a fume hood and run so as not to be exposed to the dangerous vapors.
Examiners can also use a fuming wand to expose items to the cyanoacrylate vapors. They are basically butane fueled lighters that heat small brass capsules of cyanoacrylate infused packing. These wands are typically used in the field on larger items that can not be moved or placed into the fuming chamber. Care must be taken not to inhale the vapors and a safety mask is recommended for use. Also, since the wand can get very hot you don’t want to lay it on anything flammable.
Upon development the fingerprint ridges will appear a white chalky color. In this state they may be photographed, treated with fingerprint powders and lifted, or treated with liquid dye staining reagents and photographed with an alternate light source. The impressions are much more durable than in their untreated state which means an examiner may have an opportunity to make a second or third tape lift if need be. All in all, superglue fuming is one of the most common techniques in the laboratory for processing non-porous items for fingerprints.
Most people are familiar with the concept of a Taser device but I thought it would be helpful to review some critical details. While Taser is a registered trade name you can use it to describe all devices much like you would “Xerox”. “Stun gun” is another common, albeit inaccurate, term. For the purposes of this article I will be discussing devices under the brand name Taser as most law enforcement officers will be carrying these. Tasers are technically referred to as electronic control devices (ECD). They work by generating a pulsed current through the body. They are known as less lethal devices because they temporarily interrupt normal nerve traffic impairing muscle control and motor skills.
Despite what you have seen in movies and television shows, Tasers do not render a person unconscious. They merely incapacitate them while the electrical pulses are discharged from the device. The cartridges fire two probes with small barbed points that are designed to penetrate and hold under the skin. The probes are connected to the device by fine wires that transmit the current. This allows for the pulsed electrical current to travel through the body. The key detail is that both probes have to penetrate the skin.
To that end there are a number of circumstances which may prevent this from happening. As you might imagine the probes are not as aerodynamically stable as a bullet fired from a gun. This means that a probe may miss. One may be caught up in clothing or be stopped by heavy clothing (leather belt) altogether. If both probes do not penetrate the body then the current can not complete and the device will not impair the suspect. The newest Taser devices are the X2 and X3 which provide for a second and/or third shot to be taken. This greatly increases the chances of making a good hit.
But when the current shuts off the suspect will quickly recover. This is a critical detail that should not get overlooked. The reason Taser devices are embraced by law enforcement is they have no lasting effects on a person. In a vast majority of cases the individual isn’t even taken to a hospital. Once the suspect is under control the probes are pulled out and that’s that.
Hoarding, also known as disposophobia, occurs when a person is incapable of discarding items regardless of their nature (sanitation, danger, value, etc.). While not a crime per se, it is a disturbing condition that has been a part of human culture for over a century at least. Some psychologists’ believe it is merely a symptom of an underlying mental disorder like obsessive-compulsive behavior. It has even gained some attention in the prime time media market with shows on A&E and TLC.
Most hoarders simply amass items of no value (trash, used clothing, etc.) but some may hoard specific items such as pets, books/magazines, or other items of significance to them. Hoarding can severely impair an individual or their family (although it is much more common with single adults). Aside from limiting mobility, increased fire hazard, and physical dangers, it is extremely unsanitary. Conditions like the one depicted in the photo attract a number of filth inhabiting arthropods, rodents, bacteria, and zoonotic diseases.
I had one case I which a man had filled every toilet, sink, and bathtub in his home with feces. There was feces on the walls and ceiling. He had piles of trash waist high and the kitchen floor was two feet deep in discarded food and trash. He had over 100 bottles of urine he stored next to his bed (see photo). Neighbors reported seeing the man pouring buckets of human waste in the back yard. He had a minivan in the garage that was packed so high with trash that it was un-drivable (so he bought a new car rather than cleaning out the old one).
As a writer I can see how a hoarding character can make for an interesting scene. Imagine if this hoarder had an important clue to the crime tucked away somewhere in that mess. How would the police go about finding it? What would it do to their morale? How would your characters interact with one another during the search? The possibilities are endless. Even if your character found the evidence, would it be contaminated or compromised because of its condition in hoardsville? Something to consider.
Common sense dictates that the supervisor of a crime lab actually has a solid understanding of forensics but as anyone in government will tell you…common sense is the rarest commodity. While you’ll likely find a competent forensic scientist running an accredited state or federal laboratory, the same can not always be said of the local agency. The dangers of this should be apparent. Non-scientists run the risk of making poor decisions regarding the planning, budgeting, and implementation of laboratory practices.
This is not to say that a non-scientist can not effectively supervise a crime lab; far from it. The best supervisor I ever had (Moe) knew nothing of forensics. What made him effective was that he listened to the staff and held us accountable to a set of standards. If we said we were going to do something he made sure we did. He didn’t put up with any BS but he let us be the experts we were hired to be and he had our back. I’ve also worked in a laboratory that saw a rotation of seven supervisors in just over six years! A friend of mine was once in a multi-agency debriefing for a violent murder and with a room full of people the supervisor said “I want to go over the relevance of this blood evidence but I don’t want to hear from the lab”. The problem was that she was the only bloodstain expert in the room but he just didn’t like her. Needless to say, he was a prick.
For writers this is good news. The creation of such an antagonist brings with it a natural conflict. Maybe you have a supervisor who ignores their suggestion to investigate a particular lead or process evidence in a particular way. The supervisor’s decisions may be for personal, political, or cultural reasons. Sometimes they just don’t like being upstaged by their staff and want to appear to be the “brightest bulb in the room”.
Truthfully, a lot of criminalists are type A personalities. We are confident in our abilities and often have to be advocates for our analysis (both inside and outside of the agency). Sometimes this confidence comes across as cockiness and employees outside the lab may view the criminalists as Prima Donnas. We can easily ruffle some feathers along the course of an investigation.
The point is, writing such a character can be a lot of fun. You have a lot of options as to how that interaction takes place. You may want to pick the brains of some retired CSI’s and CSI supervisors to get a better feel for the relationship dynamics. The underlying current of such a relationship is one of power/rank over knowledge/experience. If you want your antagonist to be believable you have to give them a defined motive for disagreeing with the “expert”. Maybe they think the criminalist is too young and inexperienced (sometimes they are), or maybe they just don’t respect the opinion of a woman. There can be a lot of theoretical scenarios but the field is wide open for your imagination.
Rifling is a term that refers to the grooves machined into the barrel of a firearm to impart a spin on the bullet during flight. This spin helps stabilize the bullet thereby improving accuracy and increasing the distance traveled. The raised ridges traveling along the length of the barrel are called lands and the grooves are the spaces between. These lands and grooves also have a “twist” or slight rotation to the left or right (depending on make and model) which creates the spin. The number, width, direction of twist, and rate of twist can vary between makes and models. The degree of this twist is called the “twist rate” and is expressed by how many inches it takes the projectile to make one full revolution of the rifling. For example, a barrel with a 1:12 rate of twist means the bullet will make one full revolution every 12 inches of the rifling.
Rifling is found in most modern rifles and handguns (even muzzle loaders) with the exception of most shotguns which are referred to as “smoothbore”. There are different methods for machining gun barrels but generally speaking, the tools that manufacturers use to create these lands and grooves leave unique marks (scratches) on the lands and grooves. As the bullet passes down the barrel the lands and grooves will replicate these marks onto the projectile. Firearms examiners evaluate the rifling in two main ways.
First, by looking at the gross physical features (called General Rifling Characteristics; GRC) of the lands and grooves (number, width, and direction of twist) the examiner may be able to eliminate certain makes and models of firearms. The FBI maintains a database of GRC from firearms all over the world which is updated once a year and distributed to the firearms examiner community. From this an examiner can create a list of possible gun models that share the same GRC as the crime scene bullet. When a known bullet is submitted to the lab the examiner can compare the presence and location of these rifling marks on the crime scene bullet to the known standard to determine if that gun was the one that fired the bullet. I’ll have more on this process later as it is much more detailed than what I have allowed for here.
Suffice it to say that firearms examiners use these marks to include or exclude a gun as having fired a particular bullet. If you want to put something interesting into your story choose a gun that has unusual rifling marks or general rifling characteristics. This may be from a rare or antique firearm, an after-market barrel, or a custom-made one. Your local gunsmith may be able to point you in a good direction. Then your characters can spend a few scenes trying to unravel the mystery of what kind of gun was used in the shooting. Another thing you might consider is using a gun in which these rifling marks have been damaged or destroyed intentionally by the criminal (like using a drill bit to mar the barrel). Use your imagination and have some fun with it.
Criminalists from many different forensic disciplines are routinely asked to determine if an item of evidence (unknown powder, shoe print, blood sample, cartridge case, etc) can be associated with either a group (class) or specific (individual) source. These associations may help investigators establish links between the crime scene, the parties involved, and/or the evidence. These are pretty simple concepts but even organizations like the National Academy of Sciences (NAS) can get confused about their meaning.
Class characteristics are intentional or recurring characteristics shared by one or more other objects in that group. For example, the outsole of a Nike Air Force II size 10 athletic shoe is manufactured to have a particular design. All size 10 Nike Air Force II outsoles manufactured from the same mould will have the same general appearance. It’s what distinguishes it from say a size 10 Reebok RealFlex athletic shoe. So if we find a shoe impression at a crime scene and can determine it’s a Nike Air Force II from the design elements it tells us the style of shoe but it won’t help us distinguish it from other Nike Air Force II athletic shoes of the same size.
Individual characteristics, on the other hand, are unintentional, random, and unique features of that object that distinguish it from other objects having the same class characteristics. Continuing with the footwear theme that would include specific cuts, scratches, abraded edges, foreign objects (nails), (not general wear) etc. that occur through the use and/or abuse of the footwear during its lifetime. Examiners look at the location, orientation, size, and shape of these defects to help distinguish one Nike Air Force II from another. The more individual characteristics present, the greater the degree of association (or elimination) between the evidence (impression) and the known source (shoe).
So in practical terms, if you found a shoe impression at a crime scene that showed extensive wear on the heel but the suspect shoes looked brand new then you could say that the suspect shoe did not make the impression; even though both may be of the same size, style, and manufacturer. That is not to say that class characteristics are not valuable. I won’t get into the concept of combined class characteristics here but I have seen suspects confess to crimes after being shown class character evidence i.e. “we found this Nike shoe impression at the crime scene and you’re wearing the same style Nike shoe”. Obviously they, like the NAS, don’t entirely understand the difference.
The Alternate Light Source (ALS), also referred to as a Forensic light Source is a device that transmits light through Ultra-violet (UV) range barrier filters from 190-580 nanometers. These devices are used to locate latent, i.e. invisible, evidence not seen in the visible light spectrum. They work by shining a particular wavelength of light over certain evidence which will fluoresce at that wavelength (see photo). Obviously, they are best used in darkened environments. Body fluids such as semen, urine, and saliva are one type of fluorescent evidence. Bone and teeth will also fluoresce which can be helpful during excavations. Other items like synthetic fabrics and cleaners may also fluoresce.
Blood however, will not fluoresce in absence of a reagent. In its natural state (neat) blood will absorb UV light and appear black in color. Criminalists also use an array of reagents (fingerprint powders, liquid chemical) that will fluoresce under UV light as well. Primarily these are used to develop fingerprints, footwear, or blood evidence. These reagents are designed to make it easier for the analyst to locate and document the evidence, especially on distracting multi-colored surfaces.
ALS devices can be small portable hand-held units that are easily carried around the crime scene. These units typically are of lower wattage (less bright than their large counterpart) and have fewer barrier filters to choose from. Other units like the SPEX CS-16-500 are much larger and need a 110 power source. While they can be used at crime scenes these larger units are often found in the laboratory. They have a very bright 500 watt bulb and have a range of filters throughout the UV and infra-red spectrum. These units have even been used to detect blood under four coats of paint!
Obviously, this is a device that can turn your story on a dime. For example, you may find semen on a girl’s dress or in a politician’s office. Imagine how a character might react to seeing this device being used. Because urine will fluoresce bathrooms are a real light show. Criminalists also adhere to one of the cardinal rules of professional conferences; do not check your hotel room bed sheets with a light source! Yuck. I made that mistake once and regretted it all night.
If you’re looking for an excellent book detailing the duties of the CSI first responder you need to buy “CSI for the First Responder: A Concise Guide” by Jan Lemay (CRC Press). Jan is a multiple board certified expert who breaks down the complexities of CSI work for the laymen. If you are looking for a great book for your collection this is one you can’t do without!
No, I’m not talking about your wedding anniversary (although forgetting one could lead to murder I suppose), I’m talking about anniversaries as they relate to a person’s motives. Anniversaries by their very nature denote something of importance (why else recognize them). Most are positive celebrations (religious holidays, birthdays, wedding, American Independence, etc.) but sometimes they are motivations for criminal and otherwise dark behaviors.
Anniversaries are generally perceived by the individual as either group or personal. Group anniversaries are those recognized and celebrated by numerous individuals sharing common beliefs (i.e. Catholics, Americans, Elvis fans, etc.). Group anniversaries can reflect cultural, religious, political, and natural (ex. Astrological events) events and the emotions involved in these events are typically collective. Personal anniversaries on the other hand are recognized by the individual or a very small group impacted by the event being recognized (i.e. wedding, birthday, etc.). The personal emotions and investment by members of this group are typically much stronger than group events.
Criminalists and Detectives are very aware of the anniversary motive. It can be a powerful force influencing behavior. Criminals may act upon these events for a couple of reasons. One may be to assert their allegiance to the group (terrorist organization), or their identification with the individual (Hitler, Columbine killers, death of a loved one, etc.). In fact, some law enforcement agencies have calendars of major group anniversaries and observances to help identify upcoming dates of importance.
Anniversaries are also powerful because they are predictable and recurring.
Some people experience increased emotional intensity as an anniversary looms closer. This may add a literary crescendo you can use to build up those emotions in the reader. How your character reacts to these events is entirely up to you. But the presence of an anniversary may help reveal a characters motive and explain their behavior to the reader. They may become happy and outgoing or they may become sad and reclusive. Sometimes they are even motivated to harm themselves or others. These cause and effect events add depth to a character and may lead your reader to invest more into the character or story. So consider using an anniversary motive in your story for plot or character development.