I've been reading about the U.S. Supreme Court's recent refusal to hear two challenges to victim impact videos, played for juries in the penalty phase of (usually) murder trials. It strikes me that this will, sooner or later, spawn an unforeseen and very messy response.
The relevance of such videos, presumably, is to show the jury what the family and the community have lost due to the defendant's actions. If I were a defense attorney in (especially) death penalty cases, I would consider it my duty to attempt some rebuttal of this evidence. Enter the private investigator, tasked with finding out whether (fictional example!) the young woman feeding the stray puppy in the video had had a neglected attack dog chained up behind her house, or had been spreading STD's, or was fired from a day care for molesting toddlers, or . . . .
I don't see how one can legally justify admitting the favorable video and excluding the nastier evidence. Of course, with some jurors, this approach could backfire big-time. It'd take a masterful defense attorney to pull it off.