There is such a thing as luck. It also may be true that there are so many unfound bodies in that remote location that it was inevitable that the psychic would stumble across one eventually. Also, there are some clues available to the psychic (and the police) but the psychic may be more willing to go out on a limb to interpret them and may be more able/willing to think "out of the box".
Yes, I think there are cases where people with claimed psychic test powers have been arrested on suspicion of murder because they appear to have too much knowledge of the crime to be simply guessing. I think there have also been some murderers who spent too much time trying to "help" the police by misleading them, and got caught because they ended up drawing too much attention to themselves, not because they actually got caught in a lie trying to misdirect.
Would a court regard the psychic's knowledge of the location of the body as evidence of guilt?
I think it IS evidence of guilt, but likely not anywhere near conclusive evidence. There are the old standbys, means, motive, and opportunity, which should be used to evaluate the whole case. Someone who knows too much about the case just MIGHT not be the murderer, but a witness who is afraid to come forward directly.
A psychic who knew the victim and didn't like them, was in the area at the time of the crime, doesn't have an alibi, and knows how to use whatever kind of weapon was used to kill the victim should think twice about offering their services to the police to solve that crime.
