Police departments across the United States will try to assess the final body count of the ‘Dating Game Killer’ following his death on Saturday, 24 July, with some estimates as high as 130.
Alcala, 77, died of natural causes in hospital in the San Joaquin Valley, having cheated the death penalty.
He was sentenced to death in 2010 for five grisly murders in California between 1977 and 1979, including that of a 12-year-old girl, Robin Samsoe.
Robin Samsoe’s mother claimed a pair of gold ball earrings found in Alcala's storage locker belonged to her daughter but Alcala showed a video clip from his 1978 appearance on TV show The Dating Game, in which he was wearing a similar pair.
Alcala was later sentenced to 25 years to life after pleading guilty to two homicides in New York.
He was charged in 2016 with the murder of a pregnant woman in Wyoming in 1977 but he was too ill to face trial.
Alcala is known to have travelled extensively in the United States and after his arrest detectives found in his possession more than 100 photographs of young women and girls, many of whom may have become his victims.
Authorities estimate he may have killed 130 people - mainly women and girls - around the US.
That would put him ahead of Gary Ridgway (The Green River Killer), who murdered 48 in Washington state, and Samuel Little, who died in December last year having reputedly killed 93 people over the space of four decades.
Prosecutors said Alcala stalked women like prey and took earrings as trophies.
During his trial Orange County prosecutor Matt Murphy said: "You're talking about a guy who is hunting through Southern California looking for people to kill because he enjoys it."
Bruce Barcomb, whose 18-year-old sister Jill was murdered by Alcala, said: "There is murder and rape and then there is the unequivocal carnage of a Rodney Alcala-style murder."
Alcala should have been on Death Row in San Quentin State Prison, near San Francisco, but because of his medical condition he spent most of his prison time 200 miles away at Corcoran.
The Governor of California, Gavin Newsom, has imposed a moratorium on executions. Newsom is facing a special recall election in September.