unsolved murder

U.S. murder clearance or solve rates have hit an all-time low. Experts say mutual mistrust between police and some communities is creating a vicious cycle where unsolved killings breed more mistrust.

Jennifer Carrieri's twin was shot and murdered in an empty parking lot in 1996, but nobody knows why. This year, Carrieri put up billboards in Baltimore, Md., in the hopes of solving the cold case.