Nepal's Supreme Court on Wednesday ordered the release, due to his age, of Charles Sobhraj, a French national known as "the serpent" who police say is responsible for a string of murders in the 1970s and 1980s.
Sobhraj, 78, is accused of killing over 20 young Western backpackers across Asia, usually by drugging their food or drink. He had completed 19 years of his 20-year sentence.
Known as the "bikini killer", Thailand issued a warrant for his arrest in the mid-1970s on charges of drugging and killing six women, all wearing bikinis, on a beach at Pattaya.
He was also called "the serpent" because of his ability to disguise himself following his escape from a prison in India in the mid-1980s, where he was serving 21 years on murder charges. He was later caught and jailed there until 1997.
Last year, the BBC and Netflix NFLX.O jointly produced a TV series dramatizing his crimes called "The Serpent."
Sobhraj returned to France after his release from India and in 2003 was arrested from a casino in Nepal's capital Kathmandu and later charged there for murdering American backpacker Connie Jo Bronzich. He has been held in a high-security jail in Kathmandu since 2003.
On Wednesday, Supreme Court judges Sapana Pradhan Malla and Til Prasad Shrestha ordered that Sobhraj be freed and deported from Nepal, after 19 years in prison.
"The court has ordered that if there is no other reason to keep him in jail, he should be released and sent back to his country within 15 days," the Supreme Court's spokesperson Bimal Paudel said.
Convicts sentenced to life imprisonment in Nepal usually serve 20 years in jail.
"He had already served 95% of his jail term and should have been released earlier due to his age," Sobhraj's lawyer Ram Bandhu Sharma said, adding that Sobhraj could be released from prison by Thursday.