"Before you can see the light, you have to deal with the darkness."
Analysis of a light bulb from a crashed vehicle can answer questions regarding whether the lamp was lit at the time of the crash. We will look for evidence of "hot shock" on the filament. A bulb filament with hot shock will look very differently than one that was not lit at the time of the collision. Whether or not a driver had their headlamps active or had any brake lights could become an important issue in a case.