I've been doing a lot of research on serial killers lately. Some random facts:
Luis Garavito from Colombia is thought to have killed the most people ever. Convicted of killing 138 boys, the actual number could be over 300. Most of his victims were street children. His sentence was reduced to 22 years in prison once he started helping Colombian authorities find their bodies.
Mary Ann Cotton's weapon of choice was arsenic. Believed to have killed 20 people, her victims included her mother, 4 husbands, 2 lovers, and a dozen children. She was hanged in England in 1873.
James Bulger is the oldest person on the FBI's Most Wanted list. Born in 1929, he's wanted for 19 murders and various other stuff relating to organized crime. Though he's 80 years old now, he's considered armed and dangerous.
Quite a few serial killers are from Washington state (where I live now). Among the most infamous:
The University of Washington Law student was convicted of killing 36 women in Washington, California, Utah, Colorado, and Florida. He was executed in 1989.
Kenneth Bianchi, a.k.a. The Hillside Strangler
Along with his cousin, Angelo Buono, Yates murdered 7 women in Los Angeles and 2 in Bellingham, Washington. He's currently on death row in Washington State Penitentiary.
Robert Lee Yates
Convicted of 15 murders, Yates's victims were prostitutes. He'd shoot them first and then engage in post-mortem sex. He grew up on Whidbey Island (north of Seattle) and is currently serving a life sentence in Washington State Penitentiary.
Why do I write fiction? There's no need to make this stuff up.