The Trouble With Murder Mysteries

I've mentioned that I'm writing a present-day murder mystery, largely at the request of my parents. Well, one of the problems with murder mysteries is who investigates. Specifically, in modern-day civilizations, the police investigate crime, not priests, little old ladies or even consulting detectives. If you want some amateur to investigate your crime, gymnastics will be involved.

In this case, the gymnastics are completed. My mystery has two bodies, and the police have decided that the first person killed was killed by the second murder victim, father to my POV character. My POV disagrees, and so has a reason to investigate. I've also created two strong suspects and one weak one, and the weak one actually killed both. Now I just need to write all this up.