Ron Natalie schrieb:

Presumably the gov't is immune to such influence. The major reason
that the NTSB is immune to being used in court is so that people
who provide support to the investigation know they aren't jeopardizing
pecuniary interests by doing so.

It's more than that. If it comes to a criminal investigation, then the
accused has certain rights. (A lawyer's assistance, the right to say
nothing, etc., different rights in different countries.) Now if someone
who expects to be blamed to have made a mistake in the accident and
therefore has to expect to be accused in court assists the NTSB to
investigate the case, and then later these results are used in court,
this would jeopardize his rights in court. Or, vice versa, if he wanted
to keep his rights, then he had to refuse to help the NTSB, jeopardizing
their effort to enhance safety.

Stefan