Sutcliffe initially attacked women and girls in residential areas, but appears to have shifted his focus to red-light districts because he was attracted by the vulnerability of prostitutes and the perceived ambivalent attitude, at the time, of police to prostitutes' safety. After his arrest in Sheffield by South Yorkshire Police for driving with false number plates in January 1981, he was transferred to the custody of West Yorkshire Police, which questioned him about the killings. Sutcliffe confessed to being the perpetrator, saying that the voice of God had sent him on a mission to kill prostitutes. At his trial he pleaded not guilty to murder on grounds of diminished responsibility, but he was convicted of murder on a majority verdict. Following his conviction, Sutcliffe began using his mother's maiden name of Coonan.
