A new Washington Post study finds that more than half of all murders in U.S. cities go unsolved, with a homicide arrest rate of just 49 percent. The finding is based on data from more than 50,000 homicides in 50 of the largest cities in the U.S. over the past decade. The Post also found that police investigations of murders involving white victims were significantly more likely to result in arrests than those involving black or Latino victims.