<sod >DENVER - A 70-year-old man has been arrested in the murder of a Colorado prosecutor more than 18 years after police found her dead in the bathtub of her apartment, officials said Wednesday.< eod>< sod > Colorado police believe they cracked a cold case murder after finally arresting a suspect nearly two decades after a prosecutor was found dead in the bathtub of her apartment, officials said Wednesday.< eod>