Homicidal somnambulism is the act of killing someone while sleepwalking. These are cases were someone is murdered, and the suspect states that they were sleepwalking at the time.
In one famous case, Brian Thomas age 59, who later stated he had problems sleepwalking since childhood, strangled his wife Christine. When he called emergency services, he stated,
“What have I done? I’ve been trying to wake her. I think I’ve killed my wife. Oh my God. I thought someone had broken in. I was fighting with those boys but it was Christine. I must have been dreaming or something. What have I done?…” He claimed he had mistaken his wife for an intruder, waking up to find it was his wife. He was freed in 2009 by a judge, who found him not guilty of murder.”
Is homicidal somnambulism a real thing? We know that when a patient sleeps, we can measure their brain waves and their eye movements. During a period called “non-REM sleep” (non-rapid eye movement), which is a very deep stage of sleep, sleepwalking occurs. During sleepwalking, a person can walk around but does not perceive sight, sound, smells, or even pain. If awoken, they are confused with no memory of the event.
Homicidal somnambulism has been used as a defense in a number of murders, but remains a controversial diagnosis.