With a total of more than 341,000 car crashes leading to 3,300 fatalities and 212,500 injuries in 2020, Florida ranks 3rd in the nation behind TX and CA as the most fatal state in road accidents. Hit-and-runs represent 27% of these crashes and leave the Florida Highway Patrol (FHP) and local law enforcement agencies with the challenging task of identifying the vehicle responsible for the crime. Tire marks can be found routinely due to the friction with the road surface during braking or skidding and have forensic evidentiary potential. However, anti-lock braking systems reduce these marks rendering the traditional analysis highly challenging. Nonetheless, abrasion of the tire rubber still occurs, and the rubber particles transferred to the road should be considered trace evidence. Our research focuses on using skid mark chemical composition to associate the tire that made them, solving the modern tire mark analysis challenge.
Tire rubber consists of numerous compounds providing chemical diversity beneficial to manufacturers and the field of forensics through analysis. Besides the rubber matrix (the material into which the other compounds are incorporated), many elements are introduced as oxides and traces during the manufacturing process, present either voluntarily for adjusting their performance, or involuntarily as impurities along the fabrication process. This inorganic elemental profile can become the support for the attribution of a skid mark to a tire. Forensic analysts are now familiar with the standardized use of the elemental profile for their classification or identification by Inductively Coupled Plasma–Mass Spectrometry (ICP-MS) for glass evidence. Our work is to extend this approach to tire marks for tire evidence. ICP-MS performs the chemical analysis to obtain a quantitative elemental profile of the samples over the whole periodic table. Then, statistical methods (collaboration with Dr. Larry Tang) are used to handle such large datasets to directly compare the tire mark profile to the tire samples and develop a characterization scheme.
This research introduces the international forensic community with quantitative elemental analysis of tire rubber as a new and innovative way to analyze tire skid marks and attribute to a tire. In doing so, this adds scientific credibility to a type of evidence that has seen less use in the era of intense scientific scrutiny.
- Protocol to obtain elemental profile of tire marks (Baudelet)
- Comparison between marks and tires (Baudelet, Tang)
- Field tests with Florida Highway Patrol (Baudelet)
- Lucchi J, Gluck D, Rials S, Tang L, Baudelet M. Tire Classification by Elemental Signatures Using Laser-Induced Breakdown Spectroscopy. Applied Spectroscopy. 2021;75(6):747-752. doi:10.1177/0003702821995585