The dust samples from concerned person and van in a traffic accident were identified using Fourier transform mid-infrared photoacoustic spectroscopy. The results showed that the dust spectra from the left elbow was significantly different from other locations, but was significant similar to the dust in the right side of the concerned van, which directly verified that contact occured between the concened person and van, and it provided direct evidence to allocate the responsibility in this traffic accident. Therefore, Fourier transform mid-infrared photoacoustic spectroscopy can be applied in micro analysis, which provides an alternative method in evidence analysis.