Quote Originally Posted by kwatts59

Maybe this is better
"I have seen the man who is with the girl (right now)."
That wouldn't really mean exactly the same thing though. If it did, there would be no point in us having both tenses in the first place.

"Which of those people did you see yesterday?"

"I saw the man who is with the girl".

"I have seen..." wouldn't make sense there.

In fact, we'd most likely just say "I saw the man with the girl", but without context that sentence is ambiguous and might not mean what the original poster intended to say.