As for witness statements, they aren't worth the paper they are written on.
At least two posts refer to witness statements as being worthless. This is quite incorrect. In a previous incarnation I was a Met police officer and took a great many statements - some of them from quite young people. Their accuracy was often remarkable and enabled offenders to be identified and convicted.
Much depends on the type of event being witnessed. Fast moving events are difficult and I can appreciate that a helicopter falling from the sky on a dark night will not be easy to describe. However, if a witness says it was tumbling over and over then you may be fairly certain it did not come down in a fixed orientation. And that may be of some help in understanding this tragedy.