The Economist February 1st, 2020 pp69 Forensic Science “Whendunnit?” “Fingerprints can now be dated to within a day of when they were made”
Since 1892 fingerprints have been used to identify and provide evidence to convict criminals. Often helpful, fingerprint evidence can be of lesser value when a suspect has legitimately been present in and around the location of a crime. Knowing when a print was deposited has been long sought after. When we touch a surface our skin deposits oils including a class called triglycerides (TG). Researchers studying how atmospheric oxygen modifies TG have devised a way to construct a timeline for a fingerprint deposit. Ozone, a minor form of atmospheric oxygen is most reactive with certain parts of the TG molecules resulting in new TG forms with a unique molecular signature. The native TG and new TG signature forms are measured using a most sophisticated analyzer known as MALDI. MALDI is a type of mass spectrometer that shines lasers on solids creating charged products that are then analyzed and characterized by their mass to charge ratio. Experiments using this process have been able to “time stamp” fingerprints with an accuracy of 24 hours if the prints are less than one week old. More studies are needed to confirm these findings. See the article for more detail.
Photo Credit. Beckman Coulter, Inc. Rather than clinically relevant species think forensically relevant TG species. With time native TG declines and new TG increases.