it is not because

English as a Second Language English Vocabulary, Grammar and Idioms
1

Are these sentences correct with the given meanings:

[color=red]1-It is not because someone was the last person to be seen with a murder victim that he has committed the murder.
Meaning: One can’t conclude that someone has committed a murder just because he was the last person to be seen with the murder victim.

[color=red]2-It is not because John was in this room that he has broken the vase.
Meaning: Just because John was in this room does not mean that he has broken the vase.

I don’t think they work. It seems to me that when one says ‘it is not because X that A is the case’ one proceed to give another reason why A is indeed the case.
[color=indigo]
3-It is not because John was in this room that he has broken the vase, but because five people saw him do it.

Gratefully,
Navi.

2

They don’t work primarily because they are far too wordy and complicated. No one need use them. The 3rd doesn’t work either. It indicates the reason John broke the vase is because five people were watching him.

Standard sentences to convey the same meaning:

  1. Just because someone was the last person to be seen with a murder victim doesn’t mean he committed the murder.
  2. Just because John was in the room does not mean he broke the vase.
  3. We don’t know that John broke the vase simply from the fact that he was in the room. We know because five people saw it happen.