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Future Forensics: The Problem with Biometric Guns

If you haven’t had a chance to see the latest Bond film Skyfall I highly recommend it. If you have seen it then you’re familiar with the concept of a biometric gun (also called a “smart gun”).   The idea has been around for a while but, essentially, it’s a weapon that requires a biometric (finger/palm print) scan and match from the owner in order for it to fire (other concepts include RFID chips and magnetic release). This is supposed to prevent another person from firing the gun and the idea has run the rounds in the gun control circles. It’s a swell idea on paper but, in real life it’s much more problematic.  Since it appears in a mega-blockbuster I thought you might want to keep a few things in mind should you choose to include a biometric gun in your next novel.

For law abiding citizens, a gun is a tool for self defense (sport too but that’s another topic for another day). When using a gun for self defense, simplicity of operation is preferred. The more complicated the system the more likely there will be a failure. All of us can conjure up images (from movies or television) of a crime victim grabbing a gun at the last possible second and shooting the bad guy. That may not be possible with a biometric gun due to a number of factors which I will separate into electronic, environmental, and situational categories.

First the electronics. Basically you have a digital scanner that reads the friction ridge skin pattern and compares it to the image on file. Then it has to determine a “match” before engaging the mechanical side of the gun to allow it to function. How long does this process take? How about in freezing weather? After being submerged? We’ve all had our laptop “freeze” up on us. It’s annoying but, we’re not fighting for our lives. Presumably the biometric gun operates with a battery of some type. Batteries can drain quickly in cold weather (ask any CSI about using a camera in a blizzard) and fail completely when wet. There are also concerns about impact damage. If the gun drops to the ground will the scanner crack? Will there be internal damage to the circuitry? When your life is at stake every second counts and you need a dependable mechanical weapon.

Aside form the electronics there are serious concerns about the “environment”. A biometric weapon requires a “clean” scan of the finger/palm print. Anything that interferes with the scanning will prevent the weapon from being fired. That means you can’t wear gloves (so much for cold weather use). Violent encounters/attacks also may result in bloodshed. If your hands are bloody then you can’t use the gun. Same goes for mud/dirt, grease, clothing, even water (firing underwater) may be problematic. One also presumes you have to have a flat even contact between your gun and skin which isn’t always possible. Hands can get cut open in a fight (defensive wounds) and the damaged friction ridge skin may not be recognized by the scanner. When you’re in a fight for your life you can get bloody, muddy, etc. and a finicky gun may cost you your life.

Lastly there are situational considerations. Imagine you’re in a public place when a bad guy comes in shooting. You get hit and go down injured. Your gun falls from your hand and a stranger picks it up as the bad guy advances on you. The stranger points your biometric gun at the bad guy, determined to save your life and his, pulls the trigger and…nothing. Well, not nothing. Presumably you’ll both be shot in a few seconds but you get my point. What if the guy that goes down is a police officer and you’re the by stander? Most likely the biometric gun won’t be “coded” to other friends and family and certainly not to a stranger yet, those may be the very people in a position to save your life or that of another.

So if you plan on using a biometric gun in your novel keep some of these things in mind. Gunfights are usually over in a few seconds. Of course, any one of these issues can add tension and danger to your plot line so feel free to use them. I can see your heroine trying to tear off her gloves as the rapist chases her through the park at midnight. Will she get them off before he catches her? Of course my heroine Sarah Richards will have a Glock so it won’t be an issue for her but, it might be an interesting challenge for your characters.

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.

Re-hydrating Fingerprints at the Morgue

Today I am discussing the process of obtaining fingerprints from dried up and shriveled fingers. We commonly encounter these conditions in decomposing bodies and the methods we use to re-hydrate the finger may surprise you! Check it out here.

What Does A Latent Fingerprint Card Look Like?

Placing lifting tape on card

Have you ever heard a CSI refer to a latent lift card? Chances are you have…but have you ever seen one? When CSIs develop a powdered fingerprint they have to lift it with tape. Then they affix the tape to a card which then allows the examiner to compare it without damaging it (since the powdered impression is protected by the tape). Some people think that the cards just contain fingerprints but that’s not true. Do you know what kind of information is (or should be) contained on it? A proper fingerprint lift card has two sides. Most cards are white colored about 3″ x 5″ card stock type paper. Black colored cards (glossy side) are also available for using light colored powders. Larger cards do exist for full hand or palm impressions as well but these are less commonly used. Generally the fingerprint side has a glossy finish. The other side of the card contains important information for the analyst and the courts. You see, it’s not enough to simply have a suspect fingerprint. You need to have additional value to give it any (legal) weight in court.

One important piece of information contained on the fingerprint side is what we refer to as an orientation arrow. This allows the examiner to orient the print on the object or surface it was lifted from.  This helps the examiner determine how the object was touched. Common orientations include “up” (doors/windows), “front” (vehicles), “north” (horizontal plane), or some feature of the object like “towards muzzle” (firearms).

Latent lift card with prints and orientation arrow

The back side of the card contains a lot of important case information like the case report number. This is the unique number that identifies a specific call/location/crime. There are a lot of different formats but most contain a year and sequential number of the call (i.e. 2012-1234 or the 1,234 call to police in the year 2012). The location (address) of the call is also listed. Some crimes involve multiple locations. In a bank robbery you might have evidence recovered from the bank, getaway vehicle, and suspect’s residence for example. These areas may be processed over a couple of days as well so the date and time of collection/development is also important. Was this the print developed on March 20th or April 3rd?. The examiner’s name and badge number are also important for the chain of custody.  A CSI may also make a small sketch (say of a car door window) and indicate exactly where the print was lifted. Simply saying it was collected from a window may not give an accurate picture. Was it from the top of the window or bottom? Was it on the inside (private) of the door or outside (public). All of this information is important to better evaluate the probative value of the print. A fingerprint on the outside of a victim’s vehicle may not be as suspicious as one found on the inside.

Back of lift card with case information and sketch. Notice the similar orientation arrow in sketch.

Now sometimes officers get distracted or busy and they forget to mark some or all of this information. This can cause a lot of uncertainty when evaluating the value of the evidence. Here is where it can get interesting for you as a writer. You can use this lack of information to create some uncertainty in your story. Imagine your CSI checks out evidence from a crime and finds a suspect fingerprint. But the card doesn’t say where the card was collected or who even collected it! You can’t even be sure it is associated with the crime in question because there is no case number on it. Isn’t it possible the officer mistakenly mixed it up with the cards from another case at the end of shift when they booked it into evidence? After all, how would they know right? Now this rarely happens and when it does it’s usually on a minor crime. But what if it was a homicide? You know Mr. X’s fingerprint was found, but where? Consider using that seemingly minor mistake to build a lot of tension and uncertainty in your plot.

A Peek Inside a CSI Fingerprint Kit

Have you ever wondered what was inside a fingerprint kit? One unique thing about a fingerprint kit is how dirty it gets. A CSI may have an immaculate camera bag or bloodstain collection kit but it is virtually impossible to avoid keeping a fingerprint kit clean. Kits are typically kept in a small hard shell tool box. These thing get thrown around in vehicles and scenes and it’s the best way to protect your tools and clean the outside should it get muddy or bloody. A fingerprint kit can be as varied as the examiner and most CSIs have slight differences in the types of gear they carry. Having said that, here are a few of the more common things you’ll find in a CSI fingerprint kit.

Fingerprint Case

Brushes and Wands: The fiberglass brush is the workhorse of most CSIs. They are cheap and effective. Modern ones have a plastic black handle but some older ones had a wooden handle that would eventually turn black with use. Over time these brushes will become filthy and haggard. “Cost sensitive” (i.e. ultra cheap) examiners will clean these brushes with mild soapy water but usually they are just replaced. Other specialized brushes include the traditional camel or squirrel hair (smaller brush with shorter/softer hairs) used for “fine” detail work in cleaning up the impression and the “feather duster” brush which resembles a small duster you may have at home. If you’re old enough to remember the Muppet Show think of Beaker’s hairdo. Keep in mind that a CSI will likely have a different brush for different types of powders. For example, they’ll have one fiberglass brush for black powder but a different fiberglass brush for fluorescent powders so they don’t “cross-contaminate” the powders. In addition to brushes a kit will likely contain a magnetic wand. A magnetic wand is used exclusively with magnetic fingerprint powders. The most common wands are about the size of a ball point pen but others can be larger (to hold more powder).

Inside the Kit

Various Fingerprint Brushes, Wands, and Powders

Powders: There are literally hundreds of powders available on the market. Various colors exist to provide contrast with a multitude of background colors. There are fluorescent powders of various colors which stand out at certain ultraviolet frequencies. There are even colored fluorescent magnetic powders. CSIs generally don’t carry more than a few basic types though. One of the most popular traditional powders is what we call “Bi-chromatic”. Basically it is a mix of black and grey colored powders so that developed prints will stand out on both light and dark colored surfaces. This is what most patrol officers carry as well for all their basic processing. Most CSIs carry traditional and magnetic powders in bi-chromatic or black colors. Most will also carry one general purpose jar of fluorescent powder.

Lifters and Cards: After a fingerprint is developed it needs to be lifted if possible. Basically this involves applying a clear tape to the print, lifting it off the surface (the powdered print stays on the tape) and then placing the tape on a backing card. Tape is generally 1″ to 2″ in width but larger rolls exist as well. The tape is either in a roll or in sheets about 4″ to 6″ in length. Backing cards are either glossy white (for dark powders) or black (for light colored powders). Some come with spaces on the back to fill in case information like the location, date, case #, etc. Most cards are 3″ x 5″ in size but larger ones exist for palm prints and full hand impressions.

Fingerprint Lifting Cards

Ink Pads: When we process a crime scene for fingerprints we ultimately want to make sure the prints we get are not from the residents or owners. To do this we take “elimination prints”.  Using a small ink pad like the ones you see at your bank we take fingerprints from the people on scene and transfer them to appropriate fingerprint cards or strips.

CSIs may carry other specialized equipment or supplies in their kit like UV lights, reagents, magnifiers, etc as well but the above are the basics. Another type of kit is what we call a “deceased” kit (used for taking prints of dead people) but I’ll write about that in another post.

Touring The Crime Lab: The Fingerprint Section

The fingerprint section is a workhorse of many crime laboratories and much more prevalent than DNA sections. Even small agencies, like university police departments, can have a fingerprint section. Many modern crime laboratories are divided into two broad areas; laboratory and administrative. Administrative areas include the offices or cubicles of the analysts as well as conference rooms, break rooms, etc. while laboratory areas are designed for work with hazardous materials and evidence. Most evidence is examined in the laboratory areas but latent fingerprint cards and fingerprint arrest cards (also known as 10 print cards) might be compared at the analysts desk. As such, I will talk about the fingerprint section in terms of the laboratory area and administrative area.

The Laboratory Area:

This part of the fingerprint section is where all of the physical processing takes place. Fingerprint examiners use a variety of chemical reagents and powders to develop latent fingerprints and need an area to conduct these process safely. Because powders and liquid reagents don’t mix well and the nature of air flow there are generally two types of work stations. The downdraft hood is used for powder processing.  This type of hood draws air (hence powder) down and away from the analyst. A filter system traps the powder so it doesn’t get airborne in the general laboratory area. Fingerprint powder isn’t considered really hazardous so using a hood isn’t required. It just makes things less messy.

Down Draft Fingerprint Hood

Chemical fume hood with glass shield

Chemical reagents are used under a fume hood. These hoods have a much greater air flow (at least 100 linear feet per second across the face) drawing the air up and away from the analyst. These fumes are filtered before exiting the building.  Many fingerprint sections also contain a photo station with a copy stand and alternate light source so that fingerprints can be professionally photographed as they are developed. Countertops and sinks are generally chemical resistant and dark colored in modern laboratories. Obviously you’ll also find lots of drawers and cabinets containing supplies and chemicals used in this section.

Another common piece of equipment is the superglue fuming chamber. You can see a “bank” of these cabinets behind the man in the video. These fuming chambers expose evidence to cyanoacrylate fumes thereby making the latent fingerprint visible. The fumes are very irritating and these cabinets need to be able to evacuate all of the fumes before the doors are opened.

Superglue fuming chamber

Heat plate and bottle of liquid cyanoacrylate (superglue)

The Administrative Area:

One would think that most of the work in a fingerprint section is done in the processing lab. However, examiners spend most of their time doing comparisons and computer searches through AFIS like systems. These areas may also contain printed arrest cards from suspects arrested by that agency (as well as employee fingerprint records).  This work might be done at the examiner’s desk or a shared workspace. Either way it is a typical office setting. AFIS terminals are best housed in a room separated from other sections so that the lights can be turned off. This allows the examiner to see the screen images with better clarity.

Examiner using an A.F.I.S. computer



Ear Prints At The Crime Scene?

Human Ear

Do you want to add a little used and controversial piece of evidence to your next book scene? Consider an ear print! An ear print is just like it sounds…a two dimensional impression of residue created when a human ear is pressed against a surface. Ear print evidence has been used since the early 20th Century but it has yet to gain a lot of recognition in some countries including the United States. Ear Print evidence seems to be more frequently used in Europe and perhaps other countries as well (although I’m not sure how prevalent it is in advanced countries like Australia). Here in the United States the use has been sporadic at best even though it has been admitted into evidence in several states for over a half-century.

One reason it remains controversial is that there just hasn’t been a lot of research conducted as compared to other areas of personal identification like fingerprinting or DNA. One of the most comprehensive American texts on the subject is The Iannarelli System of Ear Identification published in 1964. Earlier texts exist dating back to the early 20th Century but these are few and far between. Some believe that the structure of the external human ear (approximately 13 possible features used in a comparison) is unique and the basic anthropometric (biological measurements) values remain unchanged despite the fact that certain portions of the ear, most notably the lobe, continue to grow until death.

Ear prints are seldom found at crime scenes. In fifteen years and thousands of scenes I’ve only found two and I never had a suspect to compare them to even if I wanted to.  In one scene I found a print on the door to a safe. In the other case it was on an outside window.  I wasn’t looking for them and developed them using black fingerprint powder while looking for fingerprints. In fact, since the impressions are created by the residue on the skin most fingerprint techniques could be useful for developing an impression. One concern I have as a scientist is that of distortion.  Ear prints are made by pressing the ear to a surface. This pressure can be slight, great, or anywhere in between. Without getting too technical there is some concern about how accurate the impression “shape” under pressure is to test impressions used in a comparison. Bottom line, I think there is still more research to be done (of course, I’ve never studied these issues in depth).

As for your novel, I think ear prints could be quite interesting.  CSI’s don’t encounter them often so they may not even recognize one when they find it. The crucial part is placing one in a believable spot.  Most likely they would be found in a place where the suspect pressed their ear to listen. This could be a door, wall, window, or even someone’s chest (listening for a heart beat). It might even be from the victim. Maybe your victim was bullied or beaten at a suspect home and your investigator finds the print on the floor. You can get pretty creative but the smoother and harder the surface the better. You could even consider having a latent blood ear print that is developed with Luminol or some other reagent. Whatever you decide, have some fun with it and maybe build up some controversy over the use of the print in the investigation.

Recovering Erased Marks from White Boards

Erased Dry Board

If you work in an office or school you probably use a white “dry-erase” board. These are commonly found in a variety of settings for presenting information to a group and keeping it posted temporarily. These modern chalkboards offer the advantage of multiple bright colored inks that can be easily erased with a common chalkboard eraser pad. In fact, police agencies frequently use these boards in a “war room” to keep track of changing information during the initial hours of a major investigation. When the case is over the board is erased. To the naked eye it would appear that the information is permanently lost but to the trained CSI it is merely “hidden”. CSI’s love hidden evidence because it represents a challenge; kind of a dare on behalf of the criminal.

You see, some criminal organizations use dry-erase boards too. It might be a chop shop dealing in stolen vehicles, an illegal drug operation or prostitution ring keeping track of customers, financial, or operational (names of prostitutes and locations) information.  Sometimes the information may be patently criminal, other times it is merely another lead to be followed up on. But when the police pound on the door rest assured a criminal will be erasing the board and the information on it.  In that moment they believe they have destroyed the incriminating information.

A well trained CSI however, knows that the information is just waiting to be uncovered. You see, as the marker ink sits on the board it forms a “film”. The longer the ink stays on the board the more hardened the film becomes. When the suspect passes the eraser pad over the writing they are merely wiping off the “color” or pigment. The simplest method to develop the latent film is by the application of standard fingerprint powder with a brush, just like you would process an item for fingerprints. The best part is that the dark fingerprint powder contrasts very well with the white board making photography much easier.

Developed Writing with Black Fingerprint Powder

This processing can be done many months later as long as the board is not wiped with a liquid cleaner. This gives your detectives time to possibly chase other leads or have your protagonist come in later and save the day by discovering the evidence right in front of them. You may even use something like this as an explosive scene in a courtroom drama by exposing the new evidence mid-trial! Play around with some options and have fun with it.

Rare Genetic Mutation Prevents Fingerprint Development

Below is a very interesting video interview of a researcher in Israel who has documented a genetic mutation that prevents fingerprint patterns from being formed. The mutation is extremely rare (known to occur in only four families worldwide) and not likely to impact criminal investigations but it is interesting nonetheless. The mutation is referred to as adermatoglyphia and affects the SMARCAD1 gene which apparently regulates the formation of fingerprint patterns used for comparison. Criminals have made attempts to alter their fingerprints to avoid detection but this mutation wouldn’t leave the physical scarring that we normally associate with such events. If there were a lack of bifurcations and ending ridges then the prints couldn’t even be entered into AFIS.

Because the mutation is genetic there is the possibility that multiple family members may share the condition. That could prove very interesting for a storyline. Imagine how this condition might help members of a crime family? Imagine further if identical twins shared this mutation? They would have indistinguishable fingerprints and identical DNA!! Talk about a who-dunnit! Even if the police found clues to implicate the family it would be tough to sort out who did what by traditional forensic examinations.

If you write spy thrillers you might consider using this condition for your character as well. Imagine if an intelligence agency actually recruited individuals with this condition. For a sci-fi novel maybe someone clones individuals with this mutation for nefarious operations. You can really have some fun with it. They represent that once in a lifetime case most examiners dream of getting. I think it would make for a fascinating twist in your story.

What The Heck Is Magnetic Fingerprint Powder?

Most people are familiar with the concept of fingerprint powders even if they have never used it or had it spread all over their home. It’s cheap, usually black, messy, and pretty hard to clean up. It works well though and most basic processing kits used by CSIs and patrol officers contain a jar. Aside from black it comes in a multitude of colors (made to contrast with various backgrounds) as well as fluorescent powders for use with an alternate light source. But there is another type of fingerprint powder you may not be aware of and we call it magna-powder. Magna-powders come in all the same colors as traditional powders but what makes them different is the presence of tiny magnetic flakes embedded with the powder.

Magnetic Fingerprint Wand. The magnet is on the left end and the plunger is on the right

Magna-powder is more expensive initially but it can pay for itself over it’s lifespan. What makes magna-powder advantageous at times is that the “brush” never contacts the evidence (as it does with a fiberglass brush) which may help with fragile prints. The photo above shows one type of “wand” that is used to apply the powder to the evidence. The tip of the wand houses a magnet that “attracts” the powder to the wand holding it in place while the analyst brushes the evidence. Another great aspect of the powder is that any unused powder can be collected with the wand and placed back in the jar for processing at a future date. The examiner just pulls up on the plunger at the other end of the wand which separates the magnet from the outer housing and the powder drops back into the jar. This makes for a more effective clean-up which any home owner would appreciate.

Developing fingerprints with magna-powder

Magna-powder can be used on a variety of surfaces but I have had the best luck on plastics (like credit cards and driver’s licenses). It can also be used on paper and I have had success using it on water soaked documents that have been dried (as in recovered from lakes). Obviously using it on ferrous metals or magnetized surfaces might pose some challenges.  There’s nothing particularly special about the powders but having your characters break out a jar might give your story that extra detail that others will miss. Certainly, any readers who are in law enforcement will recognize that you’ve done some homework by picking a powder few other authors talk about.


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