As a key part of drug enforcement, identification of sources of supply and distribution patterns of illicit drugs is of major interest. For heroin a preliminary study showed significant differences among samples from disparate geographical origins (Turkey, Thailand, India, and Pakistan) via isotopic analysis of 13C. This paper discusses the applicability of the isotopic analysis of diacetylmorphine for forensic purposes by determining the isotopic fractionation due to morphine acetylation. The obtained results showed first that morphine acetylation induces an isotopic fractionation, so that the 13C enrichment of diacetylmorphine depends on both geographic origin of the sample and source of acetic anhydride used by the drug trafficker. That measurement can then be of great interest in the determination of common-batch samples (tactical intelligence purpose). Second, diacetylmorphine deacetylation has also been studied, and it appeared that this deacetylation relieves the enrichment from the acetylation-induced part; therefore, measuring morphine 13C enrichment from deacetylated heroin samples can be useful in determining the geographical origin of the samples (strategic intelligence purpose). Moreover, measuring both diacetylmorphine and morphine 13C enrichments may help identify the source of acetic anhydride used by the drug trafficker, so that the fraudulent laboratory where the morphine samples have been acetylated can be identified. 3 tables, 4 figures, and 24 references