All relevant information should be allowed to be introduced into arbitrations, trials, or other legal proceedings. No restrictions should be imposed that would limit or otherwise control the type or amount of information that any party to a legal proceeding can introduce for consideration. Furthermore, regardless of whether information was gathered legally or illegally by the police or anyone else, that information should still be entitled to be heard if it is relevant or if any party to the case wants it to be heard. Punishing the people who gathered the information illegally should be done, but it is an entirely separate matter, needing its own case and possible trial.
In addition, if information is discovered after the close of a trail that potentially has a reasonable chance of changing the outcome of that trial, the original verdict should be immediately suspended by a judge who has reviewed this new information until it has been properly assessed and processed.
No person should ever be given a second trial unless significant new evidence was found after the close of the first trial that may possibly have changed the outcome.