Examining the Digits: Uncovering Tough Clues in Crime Investigations

There are forensic scientists discovering and applying new scientific techniques to help solve cases and uncovering clues in cold cases. Since fingerprints are the most fragile pieces of evidence in a criminal investigation and are the most important to identify the perpetrator, they are the first to be located, documented, retrieved, and examined.

Some of the most common ways to retrieve a fingerprint at a crime scene is by dusting techniques, cyanoacrylate fuming (Super glue), and using various/alternate light sources. Other applications used are the Magana brush, nindydrin, silver nitrate, and amino black.

During my internship at a police forensic lab in the fingerprint section, I used the ninhydrin method (reacts with the amino acids in fingerprints) and sprayed a letter document in question to develop a print. I felt a little bit like Sherlock Holmes waiting for the print to appear. The readable print turned purple/pink in color. Then, I entered the print into the AFIS (Automatic Fingerprint Identification System), and actually got a match that resulted in an arrest. Score one for the good guys! It was quite exciting, but extremely time consuming – many days in fact. It’s definitely not like the instant results on crime dramas wrapped up in an hour. During my four-month internship in 2004, I learned how to locate, process, catalogue, and examine fingerprints. I saw fingerprints in my sleep!

In addition to various obstacles for fingerprint collection, such as weather conditions, difficult spaces, contaminated crime scenes, and a host of other problems, it can be very difficult to retrieve a “usable” print.

What happens when the print is on a difficult, non-porous surface?

Or, if the print is old?

Recovering Fingerprints on Difficult Surfaces

It’s a fact that forensic experts cannot always retrieve fingerprints, especially from non-porous surfaces and difficult objects.

Penn State professors developed a conformal coating process that can help to reveal difficult fingerprints on non-porous surfaces without altering the chemistry of the print. The researchers used a form of physical vapor deposition, which is a method that uses a vacuum and allows vaporized materials to condense on a surface creating a thin film.

Basically, this procedure helps to recover the distinct fingerprint ridges and valleys to be viewed in a topography without any changes to the print.

A huge benefit of this scientific approach would be to retrieve fingerprints from explosive devices and still be able to analyze the chemicals used in the actual device.

New Nanotech Fingerprint Analysis

Researchers in Australia and Illinois (U.S.) have discovered a new way to target the amino acids found in sweat, which can be left behind after someone touches an object. Using gold nanoparticles, scientists were able to target the amino acids on non-porous surfaces. This allows for better analysis of fingerprints because the amino acids combined with gold nanoparticles reveal a clearer, more distinguishable print.

This new fingerprint analysis method will make it easier from forensic investigators to study old, dry fingerprints, hopefully resulting in discovering new evidence in cold cases.

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We cannot underestimate today’s technology and the scientists working hard for a better understanding in forensic science and crime scene investigations. I hope that one day we can solve all our cold cases.

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