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Why We Don’t Find Fingerprints on Firearms

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As a law enforcement officer you know this is not CSI Miami, but juries love to think that what they see on television is reality. Call it the ‘CSI Effect’ or just plain nonsense, I have witnessed, and so have you, the difficulty in finding latent prints on firearms. How many times have you seen them on television obtain fingerprints off of a firearm? Too many times to count. The superglue always works in fish tank though, right?

The use of DNA in criminal investigations has become so pervasive, that we almost have forgotten about fingerprints. Fingerprints can make the claim that no two people have the same prints, something DNA cannot. Fingerprints and DNA together can make a strong argument and investigators have to remember that some chemicals used to develop prints could effect DNA analysis.

Developing latent fingerprints on firearms however, has a very low probability – somewhere around five percent. That means 95% of the time you will not find any. You wouldn’t know that by watching television. Remember, these are the same people that will be sitting on juries and evaluating what you did or didn’t do. So, you have to be prepared for the inevitable cross examination on ‘why this’ and ‘why that’ when it comes to fingerprints and firearms.

Even though obtaining fingerprints on firearms are so rare, we have to try anyway. When we are successful, we must make sure that we take photographs without and with a scale before attempting to lift them. This way, if we destroy the print upon lift, we have a scaled reference to recreate it and match it to a particular suspect.

The mindset of the crime scene technician / investigator must always be positive. If we do anything and think we will not be successful, we won’t be. We cannot force evidence to be there the same way that the defense can’t deny it’s existence when it is. It is always a best practice to conduct the search for prints and come up empty, then have to answer why you didn’t do it.

There are a number of reasons or factors that make finding fingerprints on handguns rare. These three are something investigators should remember in case they ever have to testify on why prints weren’t found on the handgun:

  • Insufficient Smooth Surfaces
  • Environment
  • Handling

Insufficient Smooth Surfaces

Many parts of a firearm were designed not to be smooth so that it doesn’t slip from the user’s hand – especially the grip. You best bet is to try on the areas most likely touched by the perpetrator: trigger, trigger guard, back strap, slide and the cartridges themselves.

Environment

The environment also plays an important role. The colder it is, the less likelihood that we will find prints. Prints are a mixture of dirt and oil from our skin and the less we sweat, the less likely prints will be left. Where the firearm was found, such as in water, mud or other similar locations also plays a role in fingerprint development.

Handling

How the perp handles the gun (or how patrol cops recover them) is vital. Placing it in their waistband, back pocket etc., can sometimes wipe prints away or make them unusable. How the firearm was secured before printing, can also alter our results. These decisions have to be made ahead of time. If you believe the firearm may have fingerprints or DNA, then securing it in a box is a better alternative than a plastic security envelope. We now know that plastic can degrade a DNA sample or smudge prints.

Next time when you have to go to court to testify and are being tortured by a defense attorney on why his client’s prints weren’t on the gun, I have now given you three plausible reasons. Ensure that each step of your investigation is carefully documented, this way we can defeat his argument. Remember, if it is not documented, then it was never done.

Now if we can only get that magic button on the computer that gives us cell phone records, photographs and location in nine seconds, we’d be all set.

Joseph L. Giacalone is a retired Detective Sergeant from the New York City Police Department, former Commanding Officer of thee Bronx Cold Case Squad, Adjunct Professor at John Jay College and author of The Criminal Investigative Function: A Guide for New Investigators, 2nd Ed. He is a media consultant on law enforcement matters, has been interviewed in numerous publications, was on A&E Television’s, The Killer Speaks, and will appear in four episodes in a new true crime show this winter for Investigation Discovery Channel.  Follow him on Twitter @JoeGiacalone and visit his website at http://www.JoeGiacalone.net


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