April 30, 2006 -- When Ann Voegtli married her husband Ron 30 years ago, she thought he was the man of her dreams -- until his dreams began to put her in danger.
"It's strange that during the day he's this kind of fun, caring person, and by night he's like this monster," Ann said.
Ron, whose condition is now under control, has a 30-year history of sleep violence, acting out his night terrors without restraint.
"Many times I thought I was crazy," Ron said. "Every night I went to bed, I knew I was going into some kind of a hell."
'Running Around Frantically'
Ron would usually jump out of bed in a rage about one hour after he fell asleep.
"His eyes are glassy, he's running around frantically; he's screaming," Ann said.
"I would just be running, running up, jumping up, going through the rooms of the house," he said, "just looking in a closet, and maybe grabbing a knife or a bat. … I was mostly running from somebody -- somebody's in the house -- looking for a weapon to protect us."
"I would stand back in the room," Ann said. "I don't want him to hurt me."
But Ann did get hurt several times when Ron hit her in bed.
"The worst had to be the night he was strangling me," she said. "He thought someone was in our apartment strangling me. But actually in reality he had his hands around my neck."
Ann screamed so loudly that Ron finally snapped out of it.
He sometimes remembered his aggression the next morning, but that didn't help him stop it at night. So he tried to get help.
"I went to a psychologist," he said. "I went to a hypnotist. I went to two sleep disorder centers. I went to a sociologist. Nobody was able to help me."
Finally, Ron was introduced to Dr. Carlos Schenck at the Minnesota Regional Sleep Disorder Center. Schenck prescribed anti-convulsant drugs, which helped get Ron's condition under control.
"He may have been running around the house like a wild maniac, but he's not a mental patient at all," Schenck said. "In the sleep lab … he demonstrated violent behavior during the delta stage of non-REM sleep. That is the stage where there is an alarm ringing in the nervous system of spontaneous, precipitous arousal that sets you off."
Even during sleep, the brain is very active. If the motor part of the brain is awake, it enables you to perform complex tasks -- you could cook, drink, or even drive. But if the monitor and memory parts of the brain are asleep, that'll disable your sense of judgment and memory during that time. In extreme cases, you could hurt someone without knowing it.
"The complex behaviors arising from non-REM sleep are the regular sleepwalking, sleep terrors," said Dr. Mark Mahowald, director of the Minnesota Regional Sleep Disorders Center and Professor of Neurology at the University of Minnesota Medical School. "These are the ones that are most often associated with murder."
Sleepwalking as a Murder Defense
Sleepwalking has been used as a defense for murder. It famously led to the acquittal of Kenneth Parks, a Canadian, in 1988. The jury believed the sleep expert's testimony that Parks was in a state of deep sleep when he jumped out of bed, drove 14 miles and killed his mother-in-law.
"The Ken Parks case is a classic example of what's called a dissociated state, meaning you have mixed wakefulness and sleep," Schenck said.
Ron is grateful what happened to Parks hasn't happened to him.
"I could have killed somebody," Ron said. "I could have killed my wife. It's possible when you're having these night terrors like that. You're out of control."
ABC News's Nancy Weiner originally reported this story for "Good Morning America Weekend Edition."