MADISON, Wis. — The majority of unsolved killings in Wisconsin over the last decade occurred in Milwaukee and involved black men as victims.

A review published Sunday by Gannett Wisconsin Media (http://post.cr/18LdYNk ) found that Wisconsin had 277 such cases between 2003 and 2012 that remain unsolved, although that left the state with a better percentage of cleared cases than the national average.

The analysis of state justice statistics showed policing agencies solved 82 percent of the 1,564 slayings during the past decade. The national clearance rate is around 65 percent.

The average victim of an unsolved killing in Wisconsin in the last decade was 33 years old. A gun was used in nearly half the cases, which investigators say typically makes it harder to solve because shooters usually avoid physical contact with their victims.

Time is crucial in wrongful death investigations. A 2011 study by the University of New Mexico found more than half of solved cases are cracked in the first 48 hours. By the time a year has passed, the probability they'll be solved drops to less than 1 percent.

But Wisconsin police officials said they never give up on cases.

"Once a case starts to get excessively old, like 20 years, you run the risk of people not remembering or being able to make identifications," said Capt. Chirs Botsch of the West Allis Police Department, which has two unsolved cases from the last decade on the books. "But then again, time may change motivations and witnesses may no longer be associated with the person they were protecting — or may have a change of heart. That's what we hope to tap into."

In Milwaukee, which has by far the most of the last decade's unsolved cases with 81 percent, a four-person cold case unit revisits 200 to 400 cases a year. The investigators resubmit dozens of DNA samples a year for cases that exceed 10 years old, to take advantage of advances in technology.