What is it about?
This study uses a highly sensitive chemical analysis technique, SIMS, to examine thin layers of residue deposited from latent - invisible - fingerprints (or fingermarks) on paper. By examining sweat residue, particularly salt content, the technique can be used to determine whether a fingermark was placed on a printed document, or whether the blank paper was handled and then printed over. Tested on a number of people and different papers, the process works even for very faint marks and for marks over a year old.
Photo by thom masat on Unsplash
Why is it important?
A lot of forensics is about identifying people, but the “when” is often as important as the “who”. Were you a customer at the bank yesterday, or there when it was robbed last night? Did you visit the flat last week, or were you there when the victim was murdered last night? Did you fake the degree certificate, or were you awarded it? Inks, fingermarks, and fingermark development agents soak into paper. This means that fingermarks can be detected many weeks after they have been deposited. Laser printing may mask a surface and stop the fingermark, or the development agent (or both) soaking into the paper. If you develop printed paper for fingermarks the mark may be obscured by the printed text, or in some cases visible through it, but this is not a good indicator of whether the fingermark or the ink was deposited first. Alternative techniques are therefore needed to put the fingermark into context. This paper offers a solution to tell if the plain paper was handled and then printed over, or was the printed paper handled.
Read the Original
This page is a summary of: Determining the chronology of deposition of natural fingermarks and inks on paper using secondary ion mass spectrometry, The Analyst, January 2014, Royal Society of Chemistry, DOI: 10.1039/c4an00811a.
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