Detection of Gunshot Residue in Blowfly Larvae, Decomposing Porcine Tissue, and Porcine Bone Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

As submitted by the proposer:
Goals and Objectives: This project will implement the use of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to distinguish projectile trauma from sharp force trauma on decomposing pig carcasses, as well as identify projectile trauma on the skeletal remains, to assist in determining the cause of death. Macroscopic identification of gunshot wound is very difficult in the late stages of decomposition due to insect activity and degradation which can modify the morphology of all trauma wounds. The presence of gunshot residue (GSR) around a wound is used to distinguish projectile trauma from sharp or blunt force trauma. Little research has been conducted concerning the retention of GSR in decomposed and skeletonized remains.

Research Design and Methods: The proposed method for GSR analysis will include a winter and summer study. Both studies involve pig carcasses inflicted with either postmortem gunshot or stab wounds. The carcasses will be placed outside in large mesh cages for a period of time to decompose. Three types of samples will be collected from all carcasses. Larvae feeding around the gunshot and stab wounds, and tissue removed from around the wounds will be collected throughout the studies to determine the presence of GSR on decomposing remains. The samples will be freeze dried and ablated with a femtosecond laser and the m/z values for elements consistent with GSR will be measured with a magnetic sector ICP-MS to determine the presence of GSR. After the carcasses are in the skeletonization stage (<50% of soft tissue remaining) the bones damaged by the bullets will be collected and analyzed for the presence of GSR. Preliminary results indicate that the samples obtained from the gunshot wounds have higher metal content consistent with GSR than the samples collected from the stab wounds, indicating the presence of GSR on the gunshot wounds.

Analysis: Measured signals will be peak area integrated and background subtracted. Results of the samples retained from the gunshot wounds will be compared to samples from the stab wounds. Multiple samples will be obtained throughout the experiment. Similar results on multiple samples will increase the validity of this work.

Reports: All data collected during this work will be consolidated and a final report will be produced and submitted to the NIJ. Dissemination of the project results will occur via publication in appropriate peer-reviewed journals and presentation at the national American Academy of Forensic Science conference.
ca/ncf