A suspect says it on every forensics TV show ... "Of course my fingerprints were at their house, I delivered a package to them earlier this week!" Soon, though, that excuse may not be enough. Using a new technique, investigators could be better able to determine how many days ago fingerprints were left at a crime scene.
The process was developed by Shin Muramoto and Edward Sisco, at the US-based National Institute of Standards and Technology (NIST). It involves using mass spectrometry to map the chemical composition of fingerprints, specifically to see which chemicals are present in what parts of the print.
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By studying fingerprints that were made on silicon wafers at known times, they realized that a substance known as palmitic acid migrates from the print ridges down into the valleys, at a predictable rate. Therefore, by observing the acid distribution in a "mystery" print, it's possible to gauge how old it is ... within reason.
So far, the technology only works on prints that are up to four days old, and that were made in laboratory conditions. The researchers plan on expanding that time frame up to 10 days or more, however, and say that it could conceivably even be used to determine how many months ago a print was left. They also plan on testing the process in real-world conditions.
Last year, scientists at the Netherlands Forensic Institute announced a fingerprint-dating technique of their own, that involves analyzing the relative amounts of certain chemicals within the prints.
A paper on the NIST research was recently published in the journal Analytical Chemistry.
Source: American Chemical Society