Forensic DNA profiling of tears stains from commonly encountered substrates

The detection and recovery of body fluid evidence to reconstruct the involvement of people in a crime is an essential step in forensic investigation. The presence of tears is extremely rare but widely misunderstood because of its nature of secretion and low volumes found. They may be secreted in cases of sexual crimes, kidnaping, and violence among many other emotionally disturbing scenarios. It is suggestive that tears are an excellent source of epithelial cells for DNA to establish identity. They are deposited on tissue paper or handkerchief and lesser common substrates include bedding, face mask, and balaclava. Trace or touch DNA can also be retrieved from used contact lenses. Since tears can be secreted due to an emotional response, they can attract forensic analysis for identification. DNA profiling from these substrates is promising in the absence of other commonly found body fluids such as blood or saliva. The current study was done to explore the use of fresh and aged tear samples for forensic DNA analysis from three different substrates i.e., tissue paper, cotton fabric, and contact lenses. STR profiles were successfully obtained from all sample types (n = 60) with 100% allele recovery. The analysis provided consistent evidence that DNA extracted using this methodology was helpful to get reliable DNA profiles for forensics comparable with that from blood or saliva for personal identification.