 Robert Hansen murdered between 15 and 21 sex workers, near Anchorage, Alaska, between 1980 and 1983.Joel Rifkin confessed to killing 17 sex workers in the New York area between 1989 and 1993, without there having been a missing persons report filed on any of the women during that time.Robert Pickton, a Canadian who lived near Vancouver, made headlines after the remains of numerous missing sex workers were found on his family farm.