As a boy, Kearns said he had night terrors and in the days leading up to the incident, he said his wife told him he had been talking in his sleep and moving around the bed.
REM behavior disorder is usually seen in much older adults. The most heinous crimes committed during sleep tend to occur in non-REM parasomnias.
Parasomnias, or sleep disorders, are some of the most misunderstood of all human behaviors, according to Rosalind Cartwright, the former director of the sleep disorder center at Chicago's Rush University Medical Center.
She has defended a host of violent characters -- burglars, cat killers and even murderers.
"They are all good people when you meet them, lovely human beings," said Cartwright, whose expertise isn't the law -- it's sleepwalking.
"Sleepwalkers can be violent," she said. "The upper frontal lobe, the most evolved part of the brain where moral teaching lives, is fast asleep."
Parks, a 23-year-old Toronto man with a wife and infant daughter, got in his car and drove 14 miles to the home of his in-laws. There, while still asleep, he stabbed to death the woman who called him the "gentle giant."
Sleepwalking is relatively common in childhood, but can be troublesome if it persists in adulthood.
About 15 percent to 20 percent of all children, both girls and boys, sleepwalk, according to the American Sleep Association. Usually it peaks around age 11 or 12 and rarely continues as they mature.
Surprisingly most violent sleepwalking occurs in the earliest part of the sleep cycle, during deep sleep, before REM (rapid eye movement) and dreams occur.
But in REM behavior disorder, sleepers like Kearns can react in direct response to a dream and hurt their bedmates.
Some researchers say it is an early precursor to Parkinson's disease.
In both REM and non-REM sleepwalking, eyes are wide open and sleepers are difficult to wake.
Usually, a sleepwalking session ends abruptly, leaving the person confused and disoriented upon waking, with no memory of the event.
Researchers say there is a genetic basis to sleepwalking -- children whose parents are sleepwalkers are two to three times more likely to go on to exhibit the same behavior.
The "architecture" of sleep looks like a skyline, according to Cartwright. As the brain begins to shut down all visual and audio input, the muscles relax and breathing is progressively slower and deeper.
In about 20 minutes the body is in deep sleep with the highest amplitude and slowest brain waves. It is during this time that walking and talking are most likely to occur. In children, those delta waves are accompanied by growth hormone.
But gradually, the deep cycle decreases and the waves have less amplitude, and after 30 minutes, the sleeper moves into the REM or rapid eye movement phase.
REM is characterized by a sudden and dramatic loss of muscle tone where the person is essentially paralyzed, except for the eyes, which dart like "ping-pong balls," breathing, and in men, erections.
It is also associated with dreaming and the blood pressure and breathing can be erratic.