I had a friend who drowned and was clinically dead, and had a NDE. She went to heaven, heard God talking to her, then she was revived and slammed back in her body. It might be relevant to note that she was a devout Catholic at the time and I daresay that would have coloured the whole experience. She gets very distressed if people question the veracity of her NDE, of the existence of heaven, of the afterlife, and of God.
Do I believe her when she tells me that this is what she experienced? Yes I do.
Do I think that she genuinely saw heaven and God, or do I think that the whole thing was a vivid hallucination produced by dying, oxygen starved brain cells? Now that, my friend, is the right question to ask.