Say person A tampers with person B's brakes, causing B's death when B misses a curve and drives off a cliff. B's family assumes it was an accident, having no reason to suspect foul play. All the same, would the car be examined for what went wrong? If so, how easy is it to detect brakes that failed due to being tampered with, rather than failed because they were merely old and worn out? (Assume the car is fairly old and worn out to start with.)
Saying it was still ruled an accident, then assume the police receive an anonymous call tipping them off about what A has done. Would this be enough to open the case as possible murder? Or would they merely call in A for questioning and see what happens? And would they definitely tell B's family about the anonymous tip, and the questioning, or would they wait until there was something substantial to go on before upsetting them with the possibility of murder? And for that matter, would the police only respond if B's family wanted to investigate and press charges? Or does the state automatically step in if murder is a possibility at all? (It would seem odd for the state to let a murderer go free just because the victim's next of kin didn't want to press charges, but for all I know it's legal.)
Assume, then, that they did call A in for questioning, and couldn't find any reason to hold him--no fingerprints or motive or anything, just the anonymous call. So they let it drop. But then say someone hears A bragging about what he did. Would that be reason enough for the police to call in A again for new questioning, or is it too flimsy? What about if someone else dies in a new crash, this time someone who had more of a connection to A? In short, what kind of proof is needed to arrest A for B's death?
Now that I have your alarmed attention, I will mention that this is for a novel I'm working on, and is not something I've ever been, or ever plan to be, involved in. :)
I do know that I'm basically a tard when it comes to legal questions, though, so you can be as condescending as you like in your answers. I seldom read crime novels--they're one of the genres that interest me least--and wouldn't usually write one, but this particular story needed an issue of life and death. Plus I figured it was about time I had an actual villain. Other than that, it's about angels and teenagers, which is the main fun part. I mean, there are no rules about angels, except the ones I make up.