Cosmo - I have been investigating serious and fatal road traffic accidents for a number of years (ex - Police). Obviously I can't relate directly to any specific a/c incidents (Taipei), not knowing circumstances.
The generally accepted principles of accident investigation (in the UK) is to find out the sequence of events which led to the incident/accident, taking into account mechanical condition, road and weather conditions, physical state of the driver, speeds etc. i.e. 'what happened'. All this obviously has to be done within the area of expertise of the investigator. Any aspects he doesn't know about, he doesn't comment.
Unless asked by the court, he makes no recommendations, and does not apportion blame. That's for the court to decide. It's the production of as much fact and reasonably supported interpretation as possible.
In the quest for truth, he is quite prepared to find against the interests of his client (which often they don't like!)
Hope this helps a little with the ethos of the investigator.
Cheers.
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Me, sweat? I'm that cool, it's condensation.