Given the entropic effects, I don't see how you are going to trace the laser from a victim. Light gets convered into heat - in a a very random fashion. You'll know it was a laser weapon, and probably (based on the effects) the power range. The beam size perhaps, maybe even the probable wavelength. That's about it.
That like saying the victim was shot with a Smith and Wesson .38.
Only a few million of them in circulation.