Neutrons in crime

The use of neutron activation analyses (NAA) as a part of police forensic work, assisting the courts in their judgments, is described. Small samples of material such as human hair, plastic packing and swabs are irradiated and then subjected to NAA. This provides a chemical fingerprint, identifying all samples of a common origin. A limitation of NAA is that only elements which emit gamma rays after irradiation can be detected while all organic material containing carbon, hydrogen, nitrogen and oxygen cannot