It really depends on the nature of my partner killing someone. If he killed someone as an act of self defence or to protect a loved one, then I would probably keep quiet or lie.
If the situation was like Maxine Carr's, then I would shop him myself. There is no reason on earth, that anyone should protect a child killer or any killer, who has killed out of greed, perversion or just out of being a nasty piece of work.
Ahhh, but that's the thing Legend- you don't know for definite.
Just because the police accuse tthem of it, it doesn't mean they did it.
You love you partner, couldn't believe they'd do such a thing, well they couldn't could they? Someone you love, with all your heart murdering? It's beyond your realms of belief.
So again...if they convinced you of their innocence, and you believed them (possibly because you really, really, really want to).
No i wouldn't. If they were genuinely innocent then i would hope that the evidence would speak for itself.
I would never forgive myself if i covered up for them and they were indeed guilty. Even if they were innocent and you gave a false alibi how would that look if you were found out.