A Study on Effects of Immersion in River Water and Sea Water on DNA Placed on Guns

To determine the quantity of DNA that can be obtained from that placed on guns after 30 minutes, 90 minutes and 270 minutes of immersion in water. Also, the aim of this study was to disclose how different types of water environments, such as freshwater and saltwater, affect the amount of DNA loss and degradation over the preset period of time. Firearms was swabbed with a double swabbing technique. DNA was isolated using a Qiagen procedure, quantified by real-time PCR, amplification was on thermal cycler and Capillary electrophoresis was performed on 3500 Genetic analyzer. The electropherograms obtained were analyzed with the GeneMapper ID-X software. Through the comparison of DNA amounts detected after isolation and DNA profiles/allele numbers detected on guns, it can be concluded that the influence of saltwater and freshwater are significantly different. The loss of DNA in saltwater from the outer firearms surface after 30 min is similar to the loss of DNA in freshwater after 90 minutes of immersion.  Based on the results of this study, especially the results of real casework sample, it can be concluded as expected that saltwater has a more serious effects on the degradation and the loss DNA on guns than freshwater. Further, it point out that the guns found in freshwater after crime could be a valuable piece of forensic evidence, whilst the guns recovered from saltwater will have less value as forensic evidence if found after more than 30 minutes