A state Supreme Court ruling means Washington voters will decide this fall whether to lower standards when it comes to prosecuting officers who kill. How big is this problem ? A recent study outlines the scope.

The study found that police killed about 8 percent of adult males who died by homicide in the U.S. That amounts to three men per day, about 1,000 per year.

Michael Esposito, who recently completed his Ph.D. at the University of Washington, coauthored the study with researchers at Cornell University and Washington University.

He told KUOW’s Angela King that the death rate is about double what could be expected from official data sources.

King: Some police departments might take issue with your findings. Why are your numbers so much higher?

Esposito: That's a big problem with data on police shootings and what kind of makes this a difficult thing for researchers to investigate. There are no actual incentives or requirements for police to report incidents of police-involved death.

There was a ProPublica article from 2014 that showed that in many states, police departments hadn't reported a shooting since 1997. So they're severely undercounting these rates. And the data that we used was a little bit more comprehensive and relied on different methods to collect that data. And it gives a better picture and a more full story.

In your study, you break things down along racial lines.

We've confirmed with our data that black men are at much higher risk than white men [of being killed by police]. Latino men were actually a little bit closer to white men. They had a slightly elevated rate but a lot of that was occurring in Southwest states.

What about Washington state?

We have estimates for the Pacific Northwest, and they're much higher than a lot of other regions in the U.S. In large metropolitan areas like Seattle, the rate for black men was about 3.4 per 100,000. For Latino men it's 1.1 per 100,000 and for whites 0.9.

Is there anything that surprised you as you started digging into these numbers?

Yes. The sheer rate of homicides that are committed by police was shocking. I mean it's 8 percent — about double what you would expect if you were using the official data sources. So that was really surprising but also I think that where these were occurring was really surprising. We usually think about these incidents as happening in large urban centers. And risk is really high there generally.

But about two-thirds of police-involved deaths happened in suburban and rural areas. And we were not expecting to find that at all.