Analyzing panel indicator bulbs in accident investigations

[anorlunda]

At 19:00 of the video below, an investigator makes the statement.

"also if you have some indication panels for example with bulbs in it, you can after a crash, you can analyze the different wires in the bulbs and then you can determine which for example indications or even warnings were active at the moment of impact."

Langauge may be a factor here. By wires, I assume he means the filaments of incandescent bulbs. Not the signal or power wires leading to the bulb.

I can imagine that a hot filament is more brittle and likely to break on impact than a cold one. But I have a hard time believing that this is a dependable method of accident investigation.

Has anyone else heard of this method? What about auto accident investigations? Has this ever been used as evidence in court?

 

[tech99]

I heard of this many years ago - I think it an old idea and used by police to find out if a car had its lights switched on in an accident.

 

[Borek]

I heard of this many years ago - I think it an old idea and used by police to find out if a car had its lights switched on in an accident.

Many years ago there was definitely such a case in Poland, police car going without lights caused an accident and state of filaments was one of the things checked during the forensic investigation (sadly, police and attorneys did everything to cover the case and to accuse people reporting that car had no lights on of false reports/statements).

 

[Baluncore]

I can imagine that a hot filament is more brittle and likely to break on impact than a cold one. But I have a hard time believing that this is a dependable method of accident investigation.

Has anyone else heard of this method?

A hot filament is stretched by the deceleration to form a large loop.
A cold filament may break away from the supports, but fragments will remain tightly coiled.
If the glass envelope breaks while the filament is hot, it will immediately oxidise.