(AP) – Kansas City police say they could solve more homicides if more witnesses would step forward with information about the killings.

Investigators typically solve about half of the city’s homicides each year. They had a 55 percent clearance rate in 2013.

Their efforts to raise that rate are hampered by reluctant witnesses, tougher suspects and blurred lines between self-defense and murder.

Last year 58 of the city’s 106 homicides were solved, with criminal charges filed in 36 cases.

Police say they usually know fairly quickly who killed someone, but without witnesses who will cooperate it’s often difficult to get enough evidence for charges.

Experts say the lifestyles of many homicide victims mirror those of their killers, making it even more difficult to crack cases.