The fingerprint will appear either masked (A) if put down before the text was printed on the paper or complete (B) if put down after the text had been printed. Credit: Loughborough University
Forensic examiners can now determine whether a fingerprint was placed on a piece of paper before or after any text was printed on it.
The technique could help resolve cases of fraud, for example where the defendant claims to have no knowledge of the document but does admit to handling the sheet of paper it was printed on while it was blank.
“Let’s say a document was found with your fingerprint on it,” said Paul Kelly of Loughborough University. “You could say that it’s there because you loaded the paper, but later someone actually printed off the document. Normal development techniques just reveal the presence of fingerprints, however, this one allows us to show that you touched the document after the text had been printed.”
Kelly developed the technique with his former PhD student, Roberto King, who is now at forensic technology company Foster+Freeman. The study was published in Scientific Reports.
Kelly said it is easy to carry out and uses common forensic tools—gelatin lifters are a standard tool of crime scene investigators. The process works by placing a thin layer of gelatin over any fingerprint that overlaps with printed text. The gelatin is then peeled away and placed inside a sealed vacuum chamber and filled with disulfur dinitride vapor, which reacts with the sample.
The fingerprint will then appear either masked (image A) if put down before the text was printed on the paper or complete (image B) if put down after the text had been printed.
One perk of the technique, said Kelly, is that it does not destroy the fingerprint or the document, meaning they could be used for further forensic testing if needed.
“Documents or artifacts that are rare or expensive or historically significant could be tested without causing any damage,” he said.
The technique was developed at Foster+Freeman’s labs based at Loughborough’s science and enterprise park, LUSEP. Both Beth McMurchie and Richard Wilson, who run the labs, are former PhD students of Kelly.
“It shows the value of partnerships based at LUSEP as all the authors came through our group at Loughborough and the work was completed at Foster+Freeman's satellite site on campus,” said Kelly. “It’s an excellent example of how PhD training, and the maintaining of close links via LUSEP can benefit everyone and produce cutting-edge results.”
Republished courtesy of Loughborough University.