From your eyes only: Efficiency of nuclear and mitochondrial DNA isolation from contact lenses at crime scenes

Recovering appropriate evidence from crime scenes to identify the perpetrator, or in certain cases, the victim, is one of the main goals of forensic investigation. The current practice includes collection of objects from which “trace” or “touch” DNA may be retrieved. Contact lenses, worn by the perpetrator/victim, represent a potentially good source of DNA. This is based on their exposure to touch DNA and the release and regeneration of epithelial cells from the eye. This study takes these premises into account with the objective of analyzing the efficiency of human nuclear and mitochondrial DNA isolation from contact lenses. DNA was collected using a non-destructive technique (double-swab) and subsequently isolated using a silica-based methodology. Although DNA quantification was variable among subjects and contact lenses, it was sufficient to amplify some STRs and successfully sequence mtDNA. The findings from this research provide a proof-of-concept that it is possible to recover, isolate, amplify human nuclear DNA, and characterize mitochondrial DNA from contact lenses left at crime scenes. These results show the potential importance of recovering unusual items from crime scenes as a potential source of DNA to identify the victim and/or suspect.