So I'm writing this script that has a main timeline and bursts of flashbacks, and one of the characters spent years keeping the secret of another, but I feel their reasons are a bit weak. So here goes: A famous author is raising his child alone, and sexually abuses her. She murders him when she's 10 years old, in what appears to be natural causes, but... a kid that age is not perfect with forensics. A 44 year old cop who is in the investigation figures stuff out, but chooses to remain silent. The kid has a feeling that cop figured it all out, but he's quiet, so she remains quiet as well. Now, the guy IS slightly crooked, and remains crooked later on even after he's out of the police force (if he wasn't crooked he wouldn't hide something this massive). But why does he hide her secret? He does it because deep down he's a nice guy who cares about her, but she IS a stranger, at least at first. Note: It can't be because he wants to extort the kid or anything like that. They start sharing a genuine caring bond years after the murder.
reason 1: he's lazy, throwing a 10 year old through the works would be a ton of paperwork. 2 - it would put his name out there, hard to fly under the radar when people know who you are. 3 - leverage, " do this or I give the cops an anonymous tip on a cold case and you go to jail" Ohhh, he could be trying to get some insurance money?
Maybe he also had an abusive parent so he's inclined to basically take her side? Honestly I don't think you need much of a reason - someone looking the other way when a child molester is murdered isn't hard to believe.
Maybe he isn't wholly bad. Or this was the kind of cop he was: an idealist who really cared about justice and honestly didn't see what could be gained by turning a 10 year old in. But the cop he is now, isn't that anymore. He's not proud of it, but deems it as necessary. Still he admires who he was, and doesn't want to do anything to tarnish that.
1/ Several posts have suggested that "sexual offender gets killed" would turn on his sympathy; my problem is, where does anybody get that idea from? If a child was with a known abusive parent, the authorities would step in. Since they haven't, we must assume that nobody knows, and it's not the kind of thing that's likely to surface during an investigation into HIS murder. Poor motive to overlook the murder. 2/ If it's the forensics that would implicate her, it wouldn't just be "a cop in the investigation" who would figure it out. Unless you've got some freaky piece of forensics that only someone with, e.g. his love of Amazonian insects, would cotton on to, it'll be something that the whole team will know, so he can't be the only one (and, presumably, a fairly lowly one) to know. To the OP; why would he keep her secret? Because he, too, is attracted to her...? Because he went to school with the author, and hates him? Because he just can't stand the way the guy's a famous author with all the SPAG and plot holes and plagiarism in his books? Because he read the author's entire canon for his English degree, and has analysed him as a pervert on the basis of his work (That gets rid of objection 1/ above!)?
A) He finds out that the girl was abused, let's say he finds photos but the girl grabs them and put them in her pocket. He realizes what those photos mean and could investigate the issue further but seeing the girl's reaction he decides to not follow that path. Also even with the photos he would not have evidence against the girl, he just THINKS that she may caused the death of her father. B) He only finds out later by slowly putting the pieces together. It could be interesting to show his struggles trying hard to avoid coming to the clear conclusion and then his dilemma when he finally realizes what happened.
