Marks involving polyvinylchloride materials in motor vehicle collisions

In collisions where there is contact between a plasticized polyvinychloride surface and a vehicle, characteristic marks arising from the plastic are deposited on the vehicle. These appear as (a) a series of ridges and depressions with embedding plastic filaments, or (b) dispersed droplets along with brown mass. The corresponding features noticed on the plastic are (a) melting and marks of stretching, and (b) dark brown discolouration and cracked film structure. These marks are dependent on whether the deformation in the collision is either melting or thermal degradation. The occurrence of the marks from melting has been reported (J. Forensic Sci., 31 (1986) 778–781). In a recent case diffenent marks, namely, dispersed droplets along with brown mass caused by the thermally degrading plastic were observed. The appearance of either of these kinds of marks on the vehicle together with corresponding features on the plastic material constitute physical evidence of contact and can be used as proof of a collision.