The Catholic church teaches that speaking in a strange (but real) language is a sign of possession.
People who believe in reincarnation think it could be a sign of that.
But this isn't a foreign language. And I do believe that deep in our memory bank, we might be able to duplicate what we can't do consciously. But that's just a theory.
That murder in Chicago was solved by the victim taking possession of a friend, definitely, and identifying the perp and things he had stolen and tried to cover with a fire. There's an article about in in the Chicago Tribune archives among other places, think it was on 60 minutes. They tried to come up with other reasons for it which was almost unprecedented.
I can tell you right now that no victim took possession of a friend. There are angels or demons, nothing else. You either go to heaven or hell, no purgatory, no anything else. The Bible is quite clear.