I'm not sure which is worse, don't look and don't know what you're giving them, or look to try to avoid restoring any questionable content and find kiddy porn and have to involve law enforcement... Be especially bad if you had to call them and it was a family member's computer.

Before SSDs became common, I quite often was asked to try and recover files from partially failed hard drives, which often required running recovery software that would find every file, even those that had been deleted but not overwritten yet. Sad to say, only about 2 computers that didn't have really nasty porn on them, and that includes jobs done for multiple members of the clergy...

I got to where I tried to avoid looking at the files if any way possible, and even spoke to a detective once to find out the best way to handle it if I ever came across anything illegal. I got lucky and never came across anything quite that bad, and am kind of glad that since SSD and cloud storage I haven't had to do a hard drive recovery in awhile.