Albert DeSalvo F. Conley said he expected investigators to find an exact match when the evidence is compared with his DNA. On July 19, 2013, Suffolk County DA Daniel F. Conley, Mass. Attorney General Martha Coakley and Boston Police Commissioner Edward F. Davis announced that DNA test results proved DeSalvo was the source of seminal fluid recovered at the scene of Sullivan's 1964 murder. Though DeSalvo was conclusively linked to Mary Sullivan's murder, doubts remain as to whether he committed all of the Boston Strangler homicides — and whether another killer could still be at large. When he confessed, people who knew
Serial killer Serial killer A serial killer is typically a person who murders three or more people, usually in service of abnormal psychological gratification, with the murders taking place over more than a month and including a significant period of time between them. Different authorities apply different criteria when designating serial killers. While most set a threshold of three murders, others extend it to four or lessen it to two. The Federal Bureau of Investigation (FBI), for example, defines serial killing as "a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone".