What if your daughter after years of abuse killed her husband but had done it in a way which she was gonna get away with it, would you hand the lassie in if you found out her guilt.
		
		
	 
First, I'm not a parent, so any speculation there would be false, as parents are guided by a lot more instinct that reason in many cases.
But, for the hypothetical, that answer is no.  I watched my mother abused for several years when I was a child. She was beaten, her nose broken, her skull cracked, and often bloodied.  It was a horror to behold as a six-year-old.  At that time, we children had mild fantasies of killing him with such a cartoonish manner as beating his brains out with a skillet.
Over time though, I recognized codependency.  Mother would not have been in that situation if she had not continued to be a victim of her own choices, her own decisions, including immorality and criminality.  She would not have deserved to die for those faults, but it didn't leave her innocent either.
If my daughter had discovered her husband was abusive and stayed after the early signs that he would not change from therapy, then she would bear part of the responsibility for staying instead of leaving.  Mother bore that responsibility, four times over for have four children dragged through all that.  It isn't even a point of bitterness, just the facts.
If retribution were taken, it would be up for a jury to decide that.  Vigilanteeism only sounds good in the abstract.  Justice is for a group to weigh and decide with due process.  I would certainly report a murder of any sort, including that of a pedophile.  I may feel it was justified, but I am not the law.  I might even take a life if I were in certain circumstances, but if I did, I'd face the justice for it, not hide like a thief (spits on the ground at the thought of thieves.)