Fingerprints – Collection and Avoidance

Fingerprints. Everyone has them and in billions of comparisons, both by humans and computers, no two prints have ever been identical. For this reason, fingerprinting has helped investigators positively identify perpetrators of crimes for over a century.

In the relatively new field of forensic science, fingerprints are arguably the oldest and most used type of forensic evidence.

How do investigators collect fingerprints and how can you avoid leaving your prints at the scene of a crime?

Forensic Methods for Collecting Fingerprints

Fingerprint Dusting

Investigators apply a fine powder to the area they are investigating. The powder will adhere to any oils left by the “friction ridges” on the skin that make up fingerprints. Dusting is very helpful when prints are left on hard surfaces.

Depending on the moisture level of the skin when the print was made, it may or may not yield a usable print an investigation and that is why other methods for retrieving fingerprints have been developed.

Ninhydrin

The chemical ninhydrin reacts with amino acids present in the sweat making latent fingerprints turning the sweat a contrasting color. This is especially useful in collecting fingerprints off paper as the sweat turns a purple color resulting in a visible fingerprint.

Superglue Fuming

In this collection method, the item you want to examine for fingerprints is placed in an airtight chamber and exposed to the fumes of heated superglue. When vaporized, the glue reacts to traces of moisture in fingerprint residue. As a result, the fingerprint turns white and becomes bonded to the surface. These types of fingerprints are easier to see and can be preserved for years.

Materials such as glass, plastic, rubber, vinyl or metal are all surfaces that superglue fuming works well to extract a usable print.

How to Prevent Leaving Your Fingerprints

The Obvious – Wear Gloves!

Cloth Gloves – These are best because they will burn easily when you are finished with the crime but the thickness of the material will lessen your sense of touch.

Rubber gloves – If you want to have the greatest sensation of touch these gloves work well, but fingerprints can be taken from the inside of rubber gloves of it is especially important that proper disposal is made.

Tape

Some criminals prefer the freedom of not wearing gloves, but still do not want to leave prints. This can be achieved by putting tape, liquid bandage or other masking agents on just the tips of their fingers.

A word of caution – if any of these masking devises come off, they are extremely difficult to see for quick retrieval and will leave your fingerprint intact for investigators. Also, you will not be protected from palm print identification.

Fingerprint Wipe Down

Another way to remove your fingerprints from a crime scene is to wipe down every surface that you touched with a cloth, BUT be forewarned, you will probably miss something because latent prints are hard to see. It is best to protect your identity from the get go.

The Extreme – Scaring

If you have committed a crime, know you have left prints and have no good reason why your prints are at the scene, the most extreme route to go is scarring your fingers by burning or cutting. If they police have copies of your fingerprints prior to the disfiguration, you could still be found guilty. Be sure you have a great story of why your hands are suddenly burned or it could look like you were “tampering with evidence.”

History of Fingerprinting

Fingerprint matching is the most commonly used forensic evidence worldwide. In fact, in most jurisdictions fingerprint examination cases match or outnumber all other forensic examination casework combined.

Fingerprints are usually taken from the underside of your finger or thumb and in some case your palm. They chart the loops, whirls and arches of your skin.

For decades, police would take an unknown print and match it with a “fingerprint card” of a known criminal. This was a tedious and long process. Unless they had a suspect to compare to the unknown, finding the criminal from a database was worse than looking for a needle in a haystack.

With the advent of the computerized database, investigators are now able to quickly compare an unknown print to millions of others in a matter of hours. This data base is known as AFIS, Automated Fingerprint Identification Systems, and was created by the FBI.

All other visible human characteristics change or can be easily altered, but fingerprints remain with you from cradle to grave.

What are your ideas for concealing fingerprints at a crime scene?

Stay Brutal!