Analyzing panel indicator bulbs in accident investigations

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Discussion Overview

The discussion revolves around the use of panel indicator bulbs in accident investigations, specifically analyzing the state of bulb filaments to determine the operational status of vehicle lights at the moment of impact. The scope includes theoretical considerations, practical applications in forensic investigations, and potential legal implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the reliability of analyzing filament state as a method of accident investigation, suggesting that a hot filament may be more brittle and likely to break on impact compared to a cold one.
  • Another participant recalls that this method has been used historically by police to determine if a vehicle's lights were on during an accident.
  • A third participant provides an anecdote about a specific case in Poland where filament state was examined during a forensic investigation, although they note issues with the investigation process itself.
  • Further elaboration on filament behavior is presented, indicating that a hot filament may stretch and form a loop upon deceleration, while a cold filament may remain coiled if it breaks away from its supports.
  • Concerns are raised about the oxidation of filaments if the glass envelope breaks while the filament is hot.

Areas of Agreement / Disagreement

Participants express skepticism about the dependability of this method for accident investigation, indicating a lack of consensus on its reliability and practical application in legal contexts.

Contextual Notes

Limitations include the assumptions about filament behavior under different conditions and the potential variability in forensic investigation practices. The discussion does not resolve the effectiveness of this method in court or its general acceptance in accident investigations.

anorlunda
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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."

language 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?

 
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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.
 
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tech99 said:
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).
 
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anorlunda said:
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.
 
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