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.