Chemical and DNA analyses yield a wealth of information from fingerprints

Palmitic acid (green) migrates from a fingerprint's peaks to its valleys. Credit: Muramoto/NIST

Advances in chemical and DNA analyses are able to glean much more information from fingerprints in the lab. Scientists have devised sensitive tests to analyze biomolecules such as amino acids and fatty acids, as well as chemicals a person may have touched, including drugs and explosives. New information revealed by chemical and DNA testing may be eventually admissible in court. 

Latent fingerprints have been used by forensic scientists to link a criminal to crime scene for over a century. New types of research can add more information to help identity crime scene fingerprints, especially if the prints are smudged or of poor quality.

Like unique fingerprint patterns, DNA can help conclusively identity individuals. In older cases, DNA extracted from archived fingerprints may be the only DNA evidence available. Black fingerprint dust and the chemical fuming did not render the DNA unusable. Instead fingerprints were protected and preserved, sandwiched between the tape and card. In the last decade scientists have developed a way to extract and concentrate minute amounts of DNA for testing. They worked with prints up to 28 years old.

Latent fingerprints contain sweat, skin cells and thousands of chemicals. Scientists are testing ways to determine biological data such as sex and age, and also what substances a person might have touched. For example, analysis has shown that amino acids are present in fingerprints at roughly twice the level in females as in males. Further testing is ongoing to be able to distinguish samples between different people regardless of sex. 

As a fingerprint ages, the chemicals deposited with the print travel from the ridges to the valleys. This observation led scientists to wonder if the phenomenon could be used to date a fingerprint. Initial research focused on the migration of fatty acids over a few days. Researchers have since been able to predict the age of the fingerprint to several months. In forensic analysis, the age of a fingerprint could be used to fix the time of a crime or rule out prints too old be relevant to a crime scene.




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