Visualization of biological traces on evidence by ninhydrin

Because of possible contamination of samples with PCR inhibitors and to avoid the typing of mixed profiles the source material for forensic DNA investigations should be collected as directly and securely as possible from the evidence. This approach requires a detectability of the source material which is often not given. The procedure introduced here using selected cases enables visualization of DNA-containing materials on evidence and hence controlled analysis. For this purpose the specimen is treated with ninhydrin. A following dye reaction verifies the presence of biological material, which possibly contains DNA. An impact on subsequent STR-analysis was not observed.