Fingerprints no longer just provide clues about an individual's identity; these oily marks can also be used to reveal a person's drug habits and potentially even his or her medical history. In research that could find applications in forensic science, immigration, and human resources—but that also raises privacy concerns—chemists are reporting a way to detect marijuana, cocaine, and methadone (used to help heroin addicts kick their addiction), as well as their metabolites, in fingerprints (Angew. Chem. Int. Ed. 2008, 47, 10167). The team, led by David A. Russell of the University of East Anglia, in England, attached antibodies that recognize drug metabolites to iron oxide magnetic particles, which forensic officers could use to dust for fingerprints. Then they appended another antibody that fluoresces to help highlight drugs and metabolites in drug-user prints. To test the technique, Russell received prints from volunteer drug users at a local clinic and detected their drug intake. The researchers previously reported a technique using antibodies attached to gold nanoparticles to detect nicotine metabolites in the fingerprints of smokers. Next up, the plan is to develop techniques for detecting disease biomarkers in prints, Russell notes.