Oftentimes there is evidence to indicate whether a vehicle's lights were on or off at the time of the collision. This is most commonly evidenced by "hot shock" or "cold shock". “Hot shock” is evidenced by deformation to the filament while it was on during an impact. "Cold shock" is evidenced by a brittle fracture while it while it was off due to an impact. More complicated issues may include circuit failures, damaged bulbs, improper wiring, aged bulbs, and more. A filament analysis can be used to determine whether a vehicle’s headlights, turn signals, taillights, and/or brake lights were on at the time of an impact.