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 revolutionary 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 whilst it was blank.

“Let’s say a document was found with your fingerprint on it,” said Professor 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.

“Of course, depending on the case, this could be good or bad for the defendant.”

Prof Kelly developed the technique with his former PhD student, Dr Roberto King, now at forensic technology company Foster+Freeman.

He said it is easy to carry out and uses common forensic tools – gelatine lifters are a standard tool of crime scene investigators.

The process works by placing a thin layer of gelatine over any fingerprint that overlaps with printed text.

The gelatine is then peeled away and placed inside a sealed vacuum chamber and filled with disulfur dinitride vapour, which reacts with the sample.

The fingerprint will then appear either masked (A - below) if put down after the text was printed on the paper or complete (B) if put down before the text had been printed.