It has gotten a lot tougher to solve murders in the United States, which currently has more than 200,000 unsolved homicides scattered around the country.

An investigation by Scripps News found a telling statistic that the U.S. Department of Justice doesn’t like to advertise: 211,000 people have been murdered since 1980 without law enforcement bringing their killers to justice.

Unsolved murder cases, referred to as cold case files, are really starting to pile up in police departments throughout the U.S. That’s because detectives are not clearing homicides like they used to do—meaning that they’re doing a poor job of making arrests that lead to placing suspects on trial for murder.

In 1965, the national homicide clearance rate was 90%. By 2012, that rate had fallen to 64%. In other words, a little more than a third of all murders in the United States today result in the arrest of the probable perpetrator.

Law enforcement in some of the country’s major cities have built an enormous backlog of cold cases due to a clearance rate that is especially low. For instance, Detroit’s police department arrested only 9% of those responsible for the city’s 386 murders three years ago. New Orleans didn’t fare much better, clearing only 15% of its 193 killings in 2012.

“The numbers of murders have increased so substantially over the years that the cold cases are overburdening many police departments,” Florida attorney Paul Marino, a retired supervisor at the Hillsborough Sheriff’s Office and chief counsel for the International Homicide Investigators Association (IHIA), told Scripps. “Active duty detectives have a never-ending run of homicides. To work older cases, they need some sort of support.”

His organization is beginning to given the matter special attention. “We are just starting to address the cold case issue,” IHIA president Mike Corrado told Scripps. “At our last national convention last year, we had a two-day breakout just on cold cases. We’ll be doing that again next year.”

-Noel Brinkerhoff, Danny Biederman

To Learn More:

How Many Unsolved Murders Are There? It's Greater Than the Population of Des Moines (by Thomas Hargrove, Scripps)

Nearly Half of All Los Angeles County Homicides Go Unsolved, Data Shows (by Sarah Favot, Pasadena Star-News)

Baltimore County Solves its Homicides; North Richmond Doesn’t (by Noel Brinkerhoff, AllGov)

Many Crimes Unsolved because of False Confessions (by Noel Brinkerhoff, AllGov)