(CNN) -- Notorious murderer Charles Manson is up for parole in California today.
Manson was sentenced in 1969 for the killings of seven people by his followers.
One man with an interest in the case is Matthew Roberts. He thinks he might be the serial killer's son.
Roberts says his birth mother had sex with Manson during a drug-fueled orgy.
He says he's been accused of cashing in on Manson's infamy, but Roberts says he just wants to know the truth.
"It has got me nothing but grief," said Matthew Roberts. "If he is my father. It would be nice to have laid eyes on him and been person to person with him once in my lifetime."
Roberts has tried to get a DNA match, but says the tests were inconclusive because Manson's sample was contaminated.