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Using Snow Print Wax

It’s Winter in Colorado which means that criminals will be leaving plenty of boot impressions in the snow. CSIs face certain challenges when dealing with snow impressions. Snow is not a forgiving medium. It is difficult to photograph due to its reflective qualities and it is even more difficult to cast in.  Snow comes in as many varieties as criminals I suspect. Some methods, like sulfur casting, may work well with certain snow packs while others do not. Sulfur casting presents it’s own challenges and many agencies seek a simpler solution to snow casting. One such method is casting with an aerosol wax commonly referred to as snow print wax.  This wax is designed to be used with dental stone. Dental stone is an excellent casting material but it can not be poured directly into the snow. It is much too heavy and as dental stone sets it generates heat.  This heat will melt the snow impression detail before the dental stone has a chance to set.

In order to use dental stone in snow you have to build a protective base layer.  This base layer will capture the detail of the impression and serve to protect it during the curing process of the dental stone. Snow print wax creates such a barrier. The wax comes in a can and is propelled by an aerosol in the same way spray paint works. Once the snow impression is photographed the reddish wax is sprayed above the impression in short sweeping motions so that the wax drifts down onto the impression. Spraying the wax directly into the impression can damage the fragile features from the force of the propellent.

Snow print wax is not perfect though…far from it. The wax can not be allowed to freeze which means you can’t leave it in your crime scene vehicle for weeks on end. Most CSIs will keep it in the lab and even lay it on the dash over the heating vents on the way to the crime scene to ensure it works properly. Even in the best of circumstances the wax may clump together and sputter larger elements onto the impression instead of a finer mist. When that happens you run the risk of damaging or obscuring details in the crime scene impression. One might wonder then, why use it at all? The simple answer is ease of use. Add to that the fact that many CSIs are not accustomed to casting in snow and it’s easy to understand why they may choose snow print wax. It’s as easy to use as spray paint.

The wax is applied to the impression one shallow layer at a time until all of the impression is covered to a depth of about an eighth of an inch. You have to spray from multiple angles to ensure that all of the snow is coated (vertical and horizontal planes). The wax is allowed to dry about five minutes between coatings and I find that four or five coatings is enough in most cases. After the final coat is allowed to dry the dental stone can be mixed (with very cold water) and gently poured into the impression.  In freezing temperatures it may take an hour or two for the dental stone to fully set. Once it has, the cast can be lifted from the snow pack and booked into evidence.

RAM Fingerprint Reagent

Fingerprint developed on pliers

Today I thought I’d cover a interesting fingerprint reagent called R.A.M. RAM is a mixture of three fairly common fingerprint reagents; Rhodamine 6G (R6G), Ardrox, and MBD 7-(P-Methoxybenzlamino-4Notrobenz-2-Oxa-1,3-Diazole). To my knowledge this reagent gained popularity in the early 1990’s and continues to see use today in many crime labs. These reagents are used to enhance fingerprints developed through superglue fuming (cyanoacrylate) followed by inspection under ultra-violet light.  All three of the above reagents comprising this mixture are used in fingerprint development so one might wonder; why mix them? Simply put, the mixture can create a broader range and intensity of reactions  making photography much easier. Of course, that was more of a concern when lasers and light sources had weaker light output (100w) compared to the units today putting out 500w. Fluorescent dye stains are very practical when processing fingerprints on multicolored non-porous surfaces because the colors of the background surface are muted under ultra-violet light and the fingerprint reagent stands out under fluorescence.

Once the evidence is fumed, the RAM can be sprayed or applied with a squirt bottle. The item can also be dipped in a tray of reagent. There is no need to rinse the item after processing with RAM. The RAM reagent is a yellow color and a little thicker than water in viscosity. Once the item is dried it is examined under ultra-violet light between 415nm and 485nm with the best results usually found at 460nm with an orange colored barrier filter. The shelf life of RAM is approximately thirty days or until certain components like petroleum ether begin to separate and will not reconstitute.

Using a squirt bottle to apply the reagent

Elevated Photography

I’ve written before about the three types of crime scene photographs. Well, those photos are the ones taken at ground level.  Photography is all about perspective and sometimes you need to get off the ground. Most of you are probably aware of aerial photographs taken from rotary or fixed wing aircraft. I’ll post something on historic and modern aerial photography soon but there is a simpler and more widely used practice to obtain a heightened perspective. We call it elevated photography. There are a number of ways to obtain an elevated perspective. All of them are dependent on the conditions on scene and the available equipment.  Of course, these techniques can also be used in the crime lab to photograph large items like bedsheets or large areas of carpet.  Here are a few examples.

The Boom:

This is a simple product marketed for crime scene investigators. Basically it’s a pole with an attachment for the camera. Fancier models also include a shutter release cable to trip the camera and take a picture. The best results require the operator to manually focus the camera lens. Since the operator can’t see through the view finder you usually have to make several test shots to achieve the one you want. These booms are typically employed in places like bathrooms or bedrooms where there is limited space or height to elevate the photographer. They can also be used to photograph objects in elevated positions like bird nests or tree limbs.

The Ladder:

The simplest is a six foot bi-fold ladder. A CSI may also use scaffolding or a taller ladder. In the extreme you might use a fire truck ladder extended out over a body or vehicle in a field. Of course, the higher you go the more risk you’re exposed to. I remember the first time I went up on a fire truck ladder. I was taking pictures of a woman’s body that was dumped in a field. There was no harness and pretty strong winds. I was pretty scared. It seemed to take hours and I couldn’t bring myself to get more than forty or fifty feet in the air. These days, safety is taken more seriously and after a few trips up you get used to it. Of course, if you hate heights you may have to call in a favor from a co-worker to take your place.

An Elevated Platform:

Any elevated position can work as well as a ladder. It may be the landing above a living room or the rooftop of an adjacent building. Some larger crime lab vans also have special roof platforms designed to accommodate a photographer. Fixed locations obviously limit the options for the photographer but they may be better than nothing.

Photo from adjacent building

Is There A Perfect Crime?

In case you missed our live chat last Friday night with the guys and gals of the Crime Writer’s Panel I thought it might be interesting to expand a little on the topic I chose to cover.  Don’t worry, the panel’s discussion will be posted to YouTube soon and I’ll tweet the link or update this page. The panel was comprised of a bunch of really talented and experienced crime writers and former law enforcement and it would be worth it to watch. There’s a good chance we’ll get together for another chat session and I’ll let you all know when that is. We spent the hour talking to fans about the inside scoop on a variety of topics in law enforcement and forensics.  The topic I chose to cover comes from one of the most frequent questions I get from crime writers; what is the perfect crime? The question always gives me a moment of pause  because I take care not to reveal sensitive information publicly. It’s a great question but, the answer may surprise you a little.

Some authors spend a lot of time trying to design the “perfect crime”. They develop intricate plots carried out by sophisticated criminals weaving plot twists and turns throughout each chapter. Real life works differently and understanding why some crimes go unsolved may help you develop a more realistic story. I’ve investigated thousands of crimes and I have yet to encounter a “sophisticated” criminal. It’s really hard to plan for every contingency, anticipate every step taken by the police. Most detectives and CSIs spend much more time studying the aspects of crime than the criminals committing them. It’s our job. To me, a perfect crime is one for which there is no evidence of it ever having happened. No evidence, no missing person, no motive, nothing. That makes for a really short book! So instead of trying to come up with your version of a “perfect crime” it may be more worthwhile to understand why some crimes go unsolved. There are basically three reasons.

Lack of Probative Evidence:

Most judicial systems require evidence to prosecute a criminal. In the United States we have a very high legal standard to meet in order to obtain a conviction. All of the burdens are placed on the prosecution.  That said, it’s kind of nice to have a little evidence to work with. The less evidence we have the harder it is to prove guilt beyond a reasonable doubt. There are two conditions that contribute to a lack of evidence. The first is limited activity. Activity creates actions and actions create evidence. Take a drive by shooting with a revolver for example. If there are no witnesses (cooperative or otherwise) then all you may have is the fired bullet. Depending on the terminal ballistics the bullet may be too mangled to retain usable rifling characteristics. Even if you were to retrieve an identifiable bullet you have to still find the gun, and from there, the shooter. This leads us to the second reason; the passage of time. Most evidence degrades to some degree with the passage of time. You may have a female victim raped and strangled in the woods but if decomposition reduces those remains to skeletal elements then you won’t likely recover DNA or other trace evidence to help identify the killer. Evidence can also be missed but, this rarely happens with seasoned investigators.

Over-abundance of Evidence:

This may sound counter-intuitive but there are times when you can have too much evidence. Consider the murder of a prostitute who was also selling drugs and stealing from her pimp. Then you find her dead. Was it one of her Johns? Her pimp? A rival drug runner or prostitute? This scenario creates multiple suspects, motives, and possible opportunities depending on the known timeline. Even if the police develop what they consider a “solid” suspect, the existence of other “possibilities” may complicate the prosecution.   In other cases you may find trace DNA that is not associated with any plausible associates. Even if you have suspect DNA in a suspicious location; the presence of “stranger” DNA may stall the prosecution. It’s not a given, just a possibility.

Misinterpretation of Evidence:

Despite what you see on television this is the least likely of reasons why crimes go unsolved. It happens. We are all human and humans are subject to making mistakes or misunderstanding evidence of an event. It may be a lack of training or maybe the detective is operating on very little sleep.  A suicide looks like an accident or a murder is staged to look like a suicide.  Staged crimes are very popular in fiction. For one reason or another I’ve had the opportunity to investigate a number of staged crime scenes. Everything from burglaries to kidnappings, to suicides,  and more. You may find this interesting but staged crimes are usually not difficult to detect. The reason is simple. Most stagers don’t understand crime the way we do but, it is always a concern.

So there you have it. Three reasons why crimes may go unsolved and therefore could be considered “perfect” crimes. These categories are very broad and may overlap. Of course, I didn’t even touch on issues like backlog, training, or time constraints but I’ll save those for another day.  The bottom line is that the universe dances to its own tune.  We can practice and study for that big recital but in the end we can’t control every outcome. Such is the nature of life and so too is the nature of death. Despite our very best efforts the deck may have been stacked against us from the beginning.

Crime Lab Tour: The Forensic Garage

Vehicle examination bays are a relatively new feature of the modern crime lab in the United States. Now there have always been garages that vehicles could be sequestered in but that was not their primary purpose. Large agencies may have used parking structures (for patrol vehicles) or impound lots but they lacked certain amenities for the forensic scientist.  When I first got into forensics we used to process vehicles at the tow yard. Some had indoor garages but others did not. In some cases they would back the cars into a kind of shipping container where you couldn’t even open the doors! Another problem is the potential for unauthorized access. Even if you lock the vehicle it’s possible for damage to occur from the normal operations of the tow yard. Workers may brush against the car wiping off fingerprints or they can accidentally hit the vehicle as they move other vehicles around. I’ve even seen cases where the suspect (owner) climbs the fence after hours and literally steals their car back from the tow yard.

A vehicle in a tow yard

A forensic garage offers certain qualities that are hard to find in other facilities such as,

  1. Security from all persons not affiliated with the investigation (including other officers and detectives)
  2. Environmental control (weather, lighting, temperature, etc.)
  3. Access to specialized tools and processing systems.

A vehicle in transit on a flatbed tow truck

Most vehicles can be processed in the field. Fingerprinting a recovered stolen vehicle with no damage may not necessitate it being towed back to the crime lab. If the car was used to kidnap and rape a woman however, it’s going to take time to process.  Some vehicles can take hours to properly search and document. It’s nice to have a safe and secure area to work in where you don’t have to worry about approaching snow storms, security, limitations of your equipment, or even the prying eyes of the media. You may have to wait hours for a search warrant to look for various kinds of trace evidence, documenting damage like impacts or bullet holes, or even restoring obliterated VIN numbers so it nice to know the vehicle is protected.  A forensic garage allows the investigator to control the environment which is critical for things like an ALS examination (light control) or the application of blood reagents like Luminol.

Looking for a bullet with a fiber optic scope

In addition to the controlled environment the garage can provide very specialized equipment such as chemical fume hoods, vehicle lifts, pneumatic tools, even a winch. Vehicle lifts are handy for getting under a vehicle to recover fired bullets, remove tires or bumpers, or even document things like damage to brake or fuel lines. It’s also nice to get under vehicles to look for blood, tissue, or clothing strips in cases of hit and run or homicide where the victim is intentionally run over. You may even find vegetation from the crime scene wedged in the undercarriage. Most garages are designed to be over sized. Large enough to house a city bus or several vehicles at once. Further, the garages are alarmed, can be easily locked down, and may even have video surveillance.  I was recently at a large garage that even had a huge tent structure that allowed the entire vehicle to be fumed with cyanoacrylate! Most forensic garages have room for two to six vehicles although some agencies may have more if they can demonstrate a need (like a regional or state crime lab).

Vehicle on a lift. Notice the chemical fume hood in the corner to the left. These are used for things like fingerprint processing with chemical reagents. The white hose is to evacuate exhaust fumes.

Pink ballistic trajectory rod in a vehicle

Bottom line is that a forensic garage is a unique feature of the modern forensic laboratory. They are nothing like the automotive garages you may be used to. They are over sized to ensure there is enough room for a photographer to be able to get the whole car in a single photograph and some even have cat walks above so elevated pictures can be taken. If you ever get a chance to tour a crime lab call ahead and see if they have a garage you can visit. Some may be off site from the main crime lab so it doesn’t hurt to ask in advance.

A view without a vehicle

Common Acronyms in Forensics

As authors, using acronyms gives a little realism to your character dialog and shows that you’ve done some basic research into the forensics profession. So I thought I would define a few of the more common acronyms used by CSIs. Don’t be shy about using these in your novel.


  1. SLR = Single Lens Reflex. The SLR is a type of camera most CSIs use. These cameras have a detachable lens that can be separated from the body. This is different than the small point and shoot cameras popular with most people.
  2. ABFO = American Board of Forensic Odontology. A very common photographic scale (ruler) is called an ABFO scale. It is “L” shaped with 6″ arms.
  3. UV = Ultraviolet. Many body fluids like semen, saliva, and urine will fluoresce under UV light and photographed even if they are invisible to the naked eye.
  4. IR = Infra-red. Infra-red light is used to detect and photograph various forms of secret writing, different inks used on the same document (like a check where someone adds extra zeros to the cash out amount), and even drugs.
  5. ALS = Alternate Light Source is a device using both ultra-violet and infrared light to discover evidence.
  6. UAV = Unmanned Aerial Vehicle. UAVs (also called drones) are becoming more popular with law enforcement agencies as a platform for taking aerial photographs and video. Basically they are sophisticated remote controlled aircraft with camera equipment that can be controlled from a ground based pilot.


  1. ACE-V = Analysis, Comparison, Evaluation, and Verification. This is the methodology used by fingerprint examiners to compare latent crime scene fingerprints to inked fingerprints on an arrest card.
  2. AFIS = Automated Fingerprint Identification System. This is a ubiquitous term used to describe a variety of computer databases that store and search fingerprint images. Don’t confuse with AFIX Tracker which is a specific brand of AFIS type computer system.
  3. I-AFIS = Integrated Automated Fingerprint Identification System. This is the national fingerprint database operated by the Federal Bureau of Investigation that can be accessed by state and local law enforcement agencies.

Crime Scenes:

  1. CSI = Crime Scene Investigator
  2. SOCO = Scenes of Crime Officer is the term for a CSI in England


  1. FMJ = Full metal jacket
  2. HP = Hollow Point

Blood Evidence:

  1. DNA = Deoxyribonucleic Acid; our genetic building blocks
  2. STR = Short Tandem Repeat is a type of modern forensic DNA testing of specific loci on two or more samples.
  3. RFLP = Restriction Fragment Length Polymorphism refers to differences between homologous DNA sequences and is an older testing procedure.
  4. CODIS = Combined DNA Index System is a computerized database of DNA profiles used in criminal investigations (similar to AFIS).
  5. BAC = Blood alcohol content.
  6. LMG = Leucomalachite green is a blood reagent with a strong odor that turns the latent bloodstain a green color. It is not commonly used today.
  7. LCV = Lueco-crystal Violet is a blood reagent that turns bloodstains a dark blue/purple color.

Drug Chemistry:

  1. GCMS = Gas Chromatograph Mass Spectrometer is a device used to identify chemical compounds in unknown samples like illicit drugs. It is a great instrument to use with mixed samples or for general screening but it will totally consume the sample.
  2. LCMS = Liquid Chromatography Mass Spectrometry is another method of drug testing that is useful in complex mixtures of samples.
  3. FTIR = Fourier Transform Infrared Spectroscopy is a devices used to test a liquid, gas, or solid substance to identify it. It is the preferred method if you want to save the sample or if you need to identify an isomer.
  4. GHB = Gamma-Hydroxybutyric acid is a common date rape drug that is both colorless and odorless. It is commonly slipped into victim’s drinks.


  1. SEM = Scanning Electron Microscope is a device using electrons rather than light to visualize very small evidence about 250 times greater than the typical light microscope.

Professional Forensic Organizations:

  1. IAI = International Association for Identification
  2. AAFS = American Academy of Forensic Sciences
  3. ACSR = Association for Crime Scene Reconstruction
  4. IABPA = International Association of Bloodstain Pattern Analysts
  5. RMABPA = Rocky Mountain Association of Bloodstain Pattern Analysts
  6. SWG = Scientific working group (several groups based on field of study like SWGTREAD,  SWGSTAIN, SWGGUN, and SWGFAST)

Don’t forget that a lot of agencies have acronyms like the FBI, DEA, BATFE, etc. Also, I have left out a number of acronyms that deal with accreditation and safety as I can’t imagine you wanting to use them in dialog (unless you want your readers to fall asleep in which case let me know!)

Crime Scene Response: The Call Out

This will be the first in a series of posts on how CSIs respond to and investigate crime scenes.  I hope that these posts will give you a little insight to the process which may help you in developing scenes and dialog in your novel. I’ll be speaking exclusively about CSIs who are on-call as opposed to those working in shifts. Obviously, if your character works a shift (like graves) they are already in uniform or in their vehicle or office and can respond accordingly. But, what about the CSIs who get called out after hours? This is where it can get a little interesting. During my career I worked banker hours during the day and was on-call at night and on weekends. Depending on the size of the lab you may be on-call as much as every other week or once every six or eight weeks. Usually you’re on call one week at a time. In some labs you may also be on “back up” the week before you go on-call which means you’re the number two person called if something major happens or the primary criminalist is already on a call out.

Most agencies will give you an on-call vehicle and some even supply your phone.  You are required to drive this vehicle everywhere you go while on-call, even on personal errands like grocery shopping or going out to eat. Of course, when the call comes you have to finish up what you’re doing and respond to the crime scene. This adds a little inconvenience to your life in that you usually have to driver separately from your family. So if you and your spouse go out for dinner you need to drive separately.  Same thing with going to the kids soccer game, Thanksgiving dinner, or anything else you might do.  You can’t take your spouse or kids to a crime scene because you don’t know how long you’ll be tied up (days in extreme cases).  Obviously, you have to stay somewhat close to home when on call. You can’t go camping for the weekend or do anything that would prevent you from responding in a reasonable amount of time. Most agencies I know of require you to be en route to a scene within thirty minutes of a call and on scene in about an hour.

Different agencies have different policies on who actually can call out a CSI. Most of the time this is restricted to the Sergeant rank or above. Since CSIs are a finite resource agencies don’t want them called out on every little thing so a higher ranked individual will evaluate the request to see if a CSI is really needed. In some agencies only the investigations supervisors can call out the lab and patrol officers must make their request through them. Either way, the CSI usually gets the call from either the ranking officer, detective, or in most cases dispatch.  Regardless, when the call comes in you have to take down pertinent information about the crime.  Every CSI will have a notebook and their phone on the nightstand or in their vehicle. Here are some of the basic things we might have to note as the call comes in.

  • Time and date of the call out
  • Who notified you
  • The crime scene location (address)
  • Initial details about the crime including secondary scenes (this information may be incomplete or incorrect depending on the source)
  • Time and place of your departure to the crime scene (this could be your residence, restaurant, or some other location)
  • Finally, time of arrival on scene.

Your departures and arrivals are usually done via police radio so there is a record. Every criminalist will be assigned a call sign number. Sometimes this is an arbitrary employee number, vehicle number,  or just your name. Here is a hypothetical radio exchange between a CSI and dispatch. When you talk to dispatch you typically only reference yourself; you don’t have to say “dispatch”. There are some websites that actually let you listen in to live police radio traffic in your area so you may want to do a web search for your local police or sheriff followed by “police radio” and see what comes up.

CSI: “651”

Dispatch: “651 go ahead”

CSI: “Show me en route to 1234 4th street from my residence”

Dispatch: “Copy 2147″ (2147 would be 9:47 pm in military time)

Then when you arrive on scene you might say…

CSI: “651 on scene”

Dispatch: “2231” (meaning your arrival is acknowledged at 10:31pm)

There is no need to acknowledge what scene you are arriving at because you already made that clear in the initial call. If you needed to talk to an officer or detective while en route you would contact them on the radio using their call sign followed by yours. For example you might say “Charlie 23, 651″. This means “hey guy named Charlie 23 this is me (651) and I want to talk to you.

Forged or Fabricated Fingerprints: What’s the Difference?

Fingerprints have played a major role in crime scene investigation for over a century. Fingerprints prove that a certain person touched a certain object and that link may have profound implications for a person’s guilt or innocence. Fingerprints are valuable to investigators because they are unique and can easily be compared by law enforcement or other investigators. These examiners use a variety of powders or chemical reagents to develop fingerprint patterns on items of evidence or at the crime scene.  Although fingerprints have become the gold standard of identification it is possible (in theory at least) to falsify this evidence and writers can use forgery or fabrication events to throw a major curve-ball   to the storyline.

The terms “forged” and “fabricated” are commonly interchanged but they are not synonymous. Let’s start with the most impractical and difficult of the two; a forgery. A forged fingerprint is created by “planting” the fingerprint of an innocent person at the crime scene or on the evidence in order to implicate them.  The easiest way to do this is to leave some moveable object containing the person’s fingerprints at the crime scene. This could include anything from a beer bottle or receipt to a weapon. It sounds simple but it is anything but.  First, a criminal has no way of knowing whether the item in question actually contains an identifiable print. Second, CSIs are used to finding prints from multiple person’s at crime scenes, especially public access scenes. Unless the fingerprint is in the victim’s blood it’s value may be somewhere between insignificant to proof of contact. For example, just because we find a fingerprint on a gun doesn’t necessarily mean that person fired the gun and likely won’t prove they fired a particular cartridge at a particular time (homicide).  Simply put, a good CSI doesn’t jump to conclusions.  I have heard concerns about another type of forgery but I have never seen it happen and don’t know anyone else who has either. It involves making a “cast” of the innocent person’s finger and then using that prop to plant prints. This idea is filled with challenges not the least of which is making a cast of a person’s finger without their knowledge or consent.  Another major challenge is that a cast won’t react to a surface in the dame way that pliable skin does and those differences can be detected when looking at a print under magnification. It sounds neat for a novel though.

“Fabrication” unfortunately have occurred in criminal investigations. Usually this is done by one of the investigators (patrol, CSI, or detective).  A “fabrication” occurs when the suspect’s fingerprint is falsely associated with a crime scene or item of evidence. For example, a crooked detective might give a suspect a soda during an interview and then lift his prints from that can. They could then put that tape lift on a card and say they lifted it from the crime scene or some other item it didn’t come from.  Another method used has been to lift an inked print from a suspect fingerprint arrest card. This too is very rare but it has happened so CSIs look for a number of things to detect such fabrications.

We look at things like surface texture, quality of print, how the tape lifted from the object in question and a number of other things I won’t reveal. Simply put, if you lifted a print from a flat hard surface but claimed it came from an uneven surface on a gun we could see that. We also may look at the actual item. For example, if you said the print was from a gun and we pull the gun out of evidence we should not only see that the gun was treated with some kind of powder but there should be an obvious spot where the lift tape removed the powder. Everything should match up in the background including the width of the tape.

CSIs also tend to mark evidence with their initials and latent lift number. For example, I may write “L2 TA” on my second latent lift on a particular item. You could then tell exactly where I lifted a particular print from on a given item of evidence. We also sometimes photograph the latents in place before we make any attempt to lift or cast them.  All of these steps help to ensure that the integrity of the fingerprint evidence is solid.

Like I said, these events are extremely rare in forensics. We take a lot of steps to ensure we have good people doing good work but it isn’t fool proof.  I’m sure there are a variety of reasons why someone may choose to commit this type of crime and there may be other evidence of dishonesty in their case work.  As you are writing scenes you might consider using forged or fabricated evidence to implicate certain characters. Even the suspicion of fabrication can add some tension until it is resolved.  Criminals are probably the most common perpetrators of these acts as they try to frame others for their crimes. Ask yourself, what other characters might have a motive, means, or opportunity  for the crime and how your criminal might exploit that.

Finding Blood Under Wallpaper

Although I am no longer in law enforcement and I don’t work on cases I still conduct research in the forensic sciences. I thought some of you might find this latest article interesting. Criminals may employ a variety of tactics to conceal forensic evidence from CSIs. Some of these efforts can be very effective while others are not. As CSIs we continually push ourselves to discover new techniques to thwart criminal efforts to conceal evidence. As authors, it pays to keep abreast of some of these techniques in your writing. In the article linked above one of the major discoveries was the false-positive reaction with one type of wall paper. This finding supports the idea that wallpapers should be removed to test for neat or latent blood staining underneath. Enjoy.

The FBI and Crime Scene Response

Anyone who knows me knows that I never pass up an opportunity to make fun of the FBI. Those same folks also know that I have a tremendous amount of respect for the agency. One of my best friends is a Special Agent and despite the fact that he is a genius, I relentlessly poke fun at him anyway.  The FBI is prominently featured in many novels, movies, and television news segments. That’s not too surprising given the agency has a well known reputation and it’s hard to miss them on the evening news (thanks to their snazzy windbreakers emblazoned with their initials).  But I have encountered a number of authors who don’t fully understand the role of the FBI in criminal investigations. Recently, an author friend had me read a scene they were working on in which the FBI was investigating an officer involved shooting.  They were under the impression that the FBI investigated all officer involved shootings.  So I thought it might be helpful to discuss when the FBI is actually involved in a case. Keep in mind that just because the FBI has jurisdiction in a crime doesn’t necessarily mean they will work the investigation. More on that in a bit.

To understand when the FBI is called in you need to understand a little about jurisdiction. Keep in mind that this issue can get very complicated so I’ll try to keep this as simple as possible. The FBI is a Federal agency within the United States of America.  I find it easiest to think of jurisdiction in two broad categories; property (location) and statutes (laws). The FBI has jurisdiction on federal properties like buildings, federal public lands (BLM, forrest, National Parks), and Indian Reservations (more on Indian Reservations in a later post).  Also included are “special” jurisdictions that don’t fit into a “normal” definition. These include places like airplanes crossing over various states (you don’t have to prove which state airspace the crime occurred in), cruise ships, and potentially even the Space Shuttle (before the program was eliminated that is). In theory, any felony and many misdemeanors on these properties could (would) be investigated by the FBI. There are two big exceptions however.  If another Federal law enforcement agency has primary jurisdiction or mission mandates over the crime. For example, the post office has its own branch that investigates mail fraud. Customs investigates smuggling and the Secret Service investigates counterfeiting and major fraud. Then there are certain crimes that may involve multiple agencies like the Drug Enforcement Agency or the Bureau of Alcohol, Tobacco, Firearms, and Explosives. Other federal reservations that are unique are military bases. See my interviews with an ARMY CID agent or NCIS Agent to get a better idea of those jurisdictions.

The second category to consider is the statute. The United States is a Federalist system comprised of Federal, state, and local laws. The FBI is a federal agency and primarily concerns itself with crimes defined under federal statutes. They won’t be responding to the average stolen vehicle.  So some of the more common crimes you may be familiar with are bank robbery (FDIC insured banks), kidnapping, public corruption, racketeering and organized crime, etc. Additionally, the FBI also deals with acts of terrorism, counter-terrorism, and a few other things I won’t mention.These activities have risen dramatically since the terrorist attacks on September 11, 2001 in New York City.  As more and more agents are preoccupied with those important tasks, local agencies are picking up the slack by handling a larger portion of things like bank robberies and kidnappings (these crimes are also against state and local law).

As if that wasn’t complicated enough the FBI can be called for assistance on any major crime. Usually these are mass murders or serial murders that may or may not cross state boundaries. It is important to recognize however that the FBI must be invited into the case by the local agency unless there is a clear violation of federal law (such as an act of terrorism). The FBI can’t just storm onto any old homicide and take over just because they want to.  More importantly, the FBI doesn’t have a dispatch center like you might find in a police department. 911 calls don’t go to the FBI switchboard and FBI agents aren’t driving around “on patrol” waiting for a radio call. Every agent I know is backlogged with major cases and doesn’t have time to investigate local crimes even if they wanted to (and they don’t).  Besides, that’s what the local police are for.

So if you plan to have the FBI investigating crimes in your novel you need to make sure that one of the following occurs. They are invited in on something major, the crime is covered under federal statutes, and that it occurs on some kind of federal property. Now, the FBI does provide a tremendous amount of mutual aid to state and local authorities via units like their crime lab, Behavioral Analysis, and Hostage Rescue to name a few but, they don’t “take over” the investigation in the process. If you are writing a typical crime novel then the FBI characters will probably be acting in these capacities (like profiling a serial killer) and not as the lead agency. Don’t be afraid to insert FBI characters, just know it may be a supporting role. Keep in mind that this is a very basic explanation of when the FBI may respond to investigations. In reality, circumstances may dictate exceptions to the rule. If you are working on a specific scene post a question and I’ll try to clarify based on your specifics.


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