I was thinking something similar the other day, when the news here was talking about how cops here in DC have upped the closure rate on murder cases significantly over the last couple of years. Turns out the overall closure rate (which I read was defined as police thinking that they have solved the case, not having someone convicted of it) was 61% out of nearly 15,000 murders in the US in 2007.
While this math is misleading, that means that there appears to be about 5,700 unsolved murders in the US, just in 2007. That just seems like an awful lot to me.
One thing you have to also consider is the cops CHOOSE what cases to work on, thus in a way are choosing which ones to solve
I read a New York Cop investigating murders has on average 10 cases open at any one time.
Well he’s gonna have to pick which ones he has the best chance of solving. Then the prosecutor also has some influence in seeing if he can actually convict someone. Then you have to add in any public sentiment and maybe time factors. A person killed from a single bullet shot at him over a huge distance at night, has few clues. A person stabbed in a violent struggle will leave more clues and needs to be acted on fast.