It is the prosecutor's job to launch an accusation if he thinks there is some data making this possible ! It is a lawyer's job to argue that this data isn't convincing. A trial will decide. Saying such a process is ridiculous seems to me... rather strange (I wouldn't like to say ridiculous, because I suppose things are working differently in other countries ; please do not fall in this US tendency saying that "if you don't do things like we do, it means you haven't still found the right way").
It's ridiculous (to me being UK based) because the whole point about aircraft investigations is that witness testimony is protected from being passed on to law enforcement agencies in the UK - i.e. aviation safety is placed above criminal proceedings. Clearly it's different in France. The reason for this is simple - if you screw up and are going to be prosecuted for it, then you are going to cover it up if there is a danger you will be locked up, hence every pilot would stay silent in any investigation in case they might be accused of a "crime".
So yes the French system does indeed appear to be different, but not for the better as far as flight safety is concerned some would argue.