Detecting Fingerprints with Lawsone

The law enforcement community is constantly looking for more sensitive techniques to sleuth out fingerprint evidence for criminal investigations. Simon W. Lewis of Curtin University of Technology, in Australia, and colleagues report that lawsone can reveal fingerprints left on paper, opening up a new class of potential detection analogs (Chem. Commun., DOI: 10.1039/b808424f). Lawsone gives henna its characteristic property for dying hair and skin reddish brown. The compound reacts with amino acids in fingerprint residues, leaving colored ridges that fluoresce at longer wavelengths than established reagents, so lawsone might help reveal details not visible to the naked eye or on surfaces where other reagents fail. Ninhydrin, the classic fingerprint reagent sensitive to amino acid residues, is still widely used on porous surfaces, but it does not fluoresce without special treatments. Jan Zonjee, a research chemist at forensic supplier BVDA International, says lawsone is not ready to replace ninhydrin, but a derivative or analog might become the reagent of choice in the future or especially good for a niche application, such as developing fingerprints on colored papers.