Ressler retired from the FBI in 1990 and authored a number of books about serial murder. He actively gave lectures to students and police forces on the subject of criminology and, in 1993, was brought in, in London, to assist in the investigation into the murders committed by
Colin Ireland. In 1995, Ressler met
South African profiler
Micki Pistorius at a conference in Scotland and she invited him to review her investigation of the "ABC Murders", so-called because of their location in the
Johannesburg suburbs of
Atteridgeville,
Boksburg, and Cleveland. A man named David Selepe had died in police custody while being investigated as a suspect for the Cleveland murders, prior to the discovery of the Atteridgeville and Boksburg crimes, and the authorities feared that they had killed an innocent man while the real culprit was still at large. Ressler believed that Selepe was indeed responsible for the Cleveland murders, either alone or with an accomplice, and that the Atteridgeville and Boksburg murders had been committed by the same offender, but that this killer was not involved in the Cleveland murders. He also pointed out that the Atteridgeville-Boksburg murderer was gaining confidence with each killing and would contact the media. As predicted, serial killer
Moses Sithole called the South African newspaper
The Star to claim responsibility for the Atteridgeville and Boksburg murders, some time after Ressler left the case. Ressler's visit to
Ciudad Juárez in Mexico to investigate the
still-active feminicides occurring there served as inspiration for the character Albert Kessler in
Roberto Bolaño's novel
2666. Ressler died at his home in Spotsylvania County, Virginia, on Sunday May 5, 2013, from
Parkinson's disease, aged 76. == Model for fictional characters ==