 These particular murders are distinguished from other murders of sex workers during the same time period due to the post-mortem mutilations that occurred, and it is for that reason that other murders of prostitutes are not usually attributed to the Ripper, or are disputed.Peter Sutcliffe (aka the Yorkshire Ripper) murdered 13 women, some of whom were sex workers, from 1975–1980 in Northern England.Gary Ridgway (aka the Green River Killer), confessed to killing 48 sex workers from 1982 to 1998, making him one of the most prolific serial killers in U.S. history.