It was a quiet night in Phoenix, Arizona, when Scott Falater stabbed his wife 44 times and held her head under water in the pool. When the police arrived, Falater said he had no memory whatsoever of the entire incident. He had, he said, been sleepwalking. Falater never denied that he had killed his wife, but he said he had no reason to do so. There were no known problems in the couple's relationship and no history of violence on Falater's part. He was convicted of murder, but many sleep experts said that his sleepwalking defense wasn't as farfetched as it seemed [source: Yuhas].
Pavor nocturnus (that's the fancy Latin name for night terrors), along with sleepwalking and confusional arousal, belongs to a subset of sleep problems referred to as "disorders of arousal." One can lead to the other. Night terrors, for instance, can turn into an episode of sleepwalking.
All of these parasomnias occur during non-REM sleep. Neuroimaging of the brain during those deep sleep cycles shows that the prefrontal cortex is dialed down to idling mode, and that's where it stays even when a person is sleepwalking. The prefrontal cortex is where we get those excellent executive functions like judgment, attention and planning. At the same time, certain pathways in the brain of somebody experiencing an episode of arousal disorder can be lit up, including those controlling sophisticated motor and emotional activities. Unfortunately that profile of switched-on, switched-off functions resembles some of the brain activity that shows up when people are violent while fully awake [source: Sicari].
Suspended somewhere between sleeping and waking, the parasomniac enjoys the worst of both worlds: fully capable of violence without any of the inhibitions that control it.
However, research has shown that violence usually occurs only when an aroused sleeper is touched [source: AASM]. The best thing to do if you see somebody experiencing an arousal disorder is to let them be.