Are criminal police reports open to the public before the crime is tried?

No. Criminal investigations take place in private, trials take place in public. If you have been accused of a crime in a state court, in most states your lawyer will be given access to the police reports well ahead of trial. This is part of a process called "discovery." By contrast, in federal cases, under a law called the Jencks Act, statements of witnesses in the possession of the police or prosecutor do not have to be turned over until after the witness testifies at trial. Many defense lawyers consider this "trial by ambush" and think this law should be changed. Of course, this does not prevent police reports from being "leaked" by "anonymous sources" or otherwise ending up being publicized by the media, particularly in high profile cases. Also, courts often hold motions hearings before trial, and details of police reports may come out during the course of these hearings.