A Study on the Effects of Immersion in River Water and Seawater on Blood, Saliva, and Sperm Placed on Objects Mimicking Crime Scene Exhibits

Abstract

ABSTRACTResponding to the great demand for genotyping evidence obtained from underwater crime scenes or Items left in water, this study was undertaken to understand the kinetics of DNA degradation on different types of biological material immersed in water. In an attempt to recreate environments currently seen at crime scenes, various objects, stained with samples of blood, sperm, and saliva, were immersed at a depth of 5 meters in a river or the sea. The effect of water was assessed from six hours immersion to three months immersion. Immersion in water was clearly shown to be the main factor in DNA degradation. Moreover, the seriousness of this degradation mainly depends on the nature of the object on which the biological sample was placed. Substrates protecting the stain such as condoms, cigarettes butts or chewing gum enable the recovery of exploitable DNA profiles after up to three months submersion. For other kinds of evidence, the DNA degradation was directly related to the time period of immersion. As a result of this work, DNA analysts can improve the cost/effectiveness ratio with evidence seized from underwater crime scenes. These concerns may be less apparent with the use of miniSTRs.