Identification of a tiny, thin and smeared dot of red paint in a fatal traffic accident case by Fourier transform-infrared microspectroscopy

Fourier transform-infrared microspectroscopy (micro-FT-IR) operated in attenuated-total-reflectance (ATR) and transmission modes following stereomicroscopy was used for the purpose of matching known and questioned paint samples in a fatal hit-and-run case. A tiny, thin and smeared dot of red paint sticking on the broken-off cross section of a side-mirror rod was taken from the victim motorcycle and referred to as the questioned sample. Two sets of red paint chips were collected as known samples from two suspect gravels trucks respectively. These were analyzed to determine whether the red paint dot found in the motorcycle could have been the transfer from one of the two gravels trucks. Although the known and questioned paint samples are in different sample forms and the grayish white polymeric background beneath the thin red paint dot somewhat interfere with the spectra comparison, the results obtained confirm the questioned red paint dot from the motorcycle and the red paint chips from one of the trucks are of the same class of paint; that is, the possibility of the paint transfer cannot be eliminated.