This undated photo provided by the Denver District Attorney's Office on Thursday, March 6, 2014 shows William Costello, defendant in a serial rape case. The office said the 48-year-old was found dead at the bottom of a multi-story parking garage Thursday. A judge declared a mistrial the case. (AP Photo/Denver District Attorney)
FILE - In this Wednesday, Jan. 29, 2014 file photo provided by the Denver District Attorney's Office suspect Michael Todd Abromovich is pictured. Abromovich, a street ministry pastor accused of posing as a U.S. Marshal and handcuffing and robbing a man he lured to a Denver motel, says he has a substance abuse problem and wants treatment. (AP Photo/Denver District Attorney's Office, File)
In this recent 2014 police mugshot photo provided by the Denver District Attorney's Office on Wednesday, Jan. 29, 2014, suspect Michael Todd Abromovich is pictured. Authorities say the Colorado man lured another man to a Denver motel with an offer of sex, then handcuffed and robbed him while posing as a U.S. marshal. (AP Photo/Denver District Attorney's Office)
Vincent Groves, seen here in an undated photo provided by the Denver District Attorney's Office, was convicted of murdering three women and died in prison in 1996. Authorities said he killed four other women between 1979 and 1988 and might be responsible for as many as 20 homicides. (Associated Press/Denver District Attorney's Office)