New evidence that we're solving more murders

Is the great decline in homicide clearance rates all a big misunderstanding?

Real world police departments are, unfortunately, much worse than their fictional counterparts at solving serious violent crimes.

A lot of that comes down to the types of offenses fiction tends to focus on. Over the past six months, I’ve read all four of Michael Connelly’s Harry Bosch novels and across all those capers in greater Los Angeles, basically only one case amounted to “guy in a gang killed another guy in a gang.” It’s of course difficult to fully characterize crimes that aren’t solved. But as best anyone can tell, a very large share of unsolved murders are the result of lethal but routine gang violence — crimes that are difficult to solve because witnesses tend not to cooperate, and where even if authorities are pretty sure Crew X did this shooting and Crew Y did that shooting, they still need to identify a specific trigger man to close the case.

At any rate, a lot of unsolved murders stay unsolved. And as anyone who’s ever looked up clearance rates knows, not only are there a lot of unsolved murders, but clearance rates have fallen precipitously over time.

This is normally taken as a sign of falling police productivity. Either witnesses are becoming less cooperative, murderers are getting better at avoiding detection (by using guns, for example), or detectives are getting less skilled. Another interpretation is that Warren Court jurisprudence made it harder for investigators to crack cases. Or perhaps it’s the opposite, and prosecutors used to railroad innocent people but now they don’t.

An important new article available now in pre-print from the Annual Review of Criminology suggests that this is all wrong.

Instead, in “The Sixty-Year Trajectory of Homicide Clearance Rates: Toward a Better Understanding of the Great Decline,” Duke’s Philip J. Cook and the University of South Carolina’s Ashley Mancik argue that the decline in clearance rates is completely benign.