Charles Manson is shown during an interview in 1989. Manson applied for and received a marriage license in November to wed Afton Elaine "Star" Burton, but it is set to expire unused this week. Reuters

Convicted mass murderer Charles Manson has run out of time to wed his 27-year-old girlfriend -- for now. The couple, which applied for and received a 90-day marriage license in November, has not yet exchanged vows. Their license doesn't expire until Thursday, but inmate weddings are only allowed on weekends, California Department of Corrections and Rehabilitation spokeswoman Terry Thornton told the Los Angeles Times. “A Manson wedding did not take place,” she said, adding that she could not speak as to why the couple had not married.

Eighty-year-old Manson is serving out a life sentence in the all-male Corcoran State Prison near Fresno, California. The cult leader has been incarcerated since a 1971 jury convicted him and his "family" of killing seven people, including actress Sharon Tate, in 1969. Authorities have rejected Manson's requests for parole 12 times, most recently in 2012. His next chance to get out is scheduled for 2027, at which time Manson will be 92 years old.

Manson's girlfriend, Afton Elaine "Star" Burton, has said she wants to marry him in order to better work on his case. Burton regularly updates websites claiming Manson is innocent, the Washington Post reported, and has been writing him fan letters for nearly a decade.

The nature of the couple's relationship is unclear. In 2013, when Burton told Rolling Stone they were getting married, Manson denied it, saying "That's a bunch of garbage ... We're just playing that for public consumption." But after Kings County issued their marriage license last year, plans to tie the knot seemed back on. "Y'all can know that it's true," Burton told the Associated Press. "It's going to happen."

Although it hasn't happened yet, Burton reportedly wanted to move forward with the wedding. Her friend, New York photo editor James McGrath, told the AP that she planned to get another license and finally marry Manson.