Ehleringer, J.R., D.A. Cooper, M.J. Lott and C.S. Cook. 1999. Geo-location of heroin and cocaine by stable isotope ratios. Forensic Science International 106:27-35.

Analyses of the carbon and nitrogen stable isotope ratios in heroin and cocaine samples obtained from different geographic regions indicated stable isotope ratio combinations that were strongly correlated with geographic location. Further analyses of the isotope ratios of morphine derived from the deacetylation of heroin exhibited more pronounced isotopic differences among regions, increasing its potential as a tool for geo-location and for sample-to-sample comparison.