Prosecutors have dropped charges against Sture Bergwall, previously known as Thomas Quick, in the last of eight murder convictions against him.
"It is an incredible relief. It has been a long, drawn-out review process with some strange twists and turns from Supreme Court justices and others," Bergwall tells Swedish Radio News.
Courts had already overturned seven of the eight murder convictions against Bergwall in what became one of Sweden's longest-running legal cases.
Writing on his blog following today's annoucement, Bergwall said: "Today is a day of joy and a day for reflection."
Bergwall told tabloid Aftonbladet that therapy and drug treatments caused him to confess to the murders. He claimed that he was given "unlimted amounts" of narcotics while in psychiatric care.
Bergwall has also called for a "responsibility commission" into the legal process against him.
"The responsible individuals and institutions need to be identified," he said.
The eighth murder case concerned Charles Zelmanovits who disappeared after a school dance in Piteå, northern Sweden in 1976. His body was found in 1983.
Bergwall, 63, confessed to the eight murders to his therapist in 1994, while he was in psychiatric care, leading him to be described as Sweden's "worst serial killer of modern times".
He was convicted of the string of murders between 1994 and 2001, largely on the strength of his confessions and without forensic evidence. Bergwall withdrew his confessions in 2008.
He is still in psychiatric care, but told Swedish Radio News on Tuesday that he is "convinced" he will be released soon.
Bergwall has a long history of mental illness, abuse and violence before he was convicted of murder.
In 1969 he first received care after sexually assaulting four boys. Five years later he stabbed a man in Uppsala, after which his therepy resumed.
And in 1990, Bergwall and an accomplice took a bank manager and his family hostage, and made off with large sums of money. Bergwall was again sentenced to psychiatric care following this incident.