Sleepwalking can sometimes result in injury, assault, or the death of someone else. For this reason, sleepwalking can be used as a legal defense. However, sleepwalking is a difficult case to prove.[31] It is impossible to prove absolutely that a crime occurred in the context of a sleepwalking episode because there is no objective means to assess it retrospectively. It relies on probability and circumstantial evidence of a behavior that often has no witnesses (including the defendant, because amnesia is a feature of sleepwalking). Even a history of sleepwalking does not support that it was a factor during any given event. Alternative explanations, such as malingering and alcohol and drug-induced amnesia, need to be excluded. The differential diagnosis may also include other conditions in which violence related to sleep is a risk, such as REM Sleep Behavior Disorder (RSBD), fugue states, and episodic wandering."[32] In the 1963 case Bratty v Attorney-General for Northern Ireland, Lord Morris stated, "Each set of facts must require a careful examination of its own circumstances, but if by way of taking an illustration it were considered possible for a person to walk in his sleep and to commit a violent crime while genuinely unconscious, then such a person would not be criminally liable for that act."[33] In the case of the law, an individual can be accused of non-insane automatism or insane automatism. The first is used as a defense for temporary insanity or involuntary conduct, resulting in acquittal. The latter results in a "special verdict of not guilty by reason of insanity."[34] This verdict of insanity can result in a court order to attend a mental institution.[35] Other examples of legal cases involving sleepwalking in the defense include: 1846, Albert Tirrell used sleepwalking as a defense against charges of murdering Maria Bickford, a prostitute living in a Boston brothel. 1981, Steven Steinberg, of Scottsdale, Arizona was accused of killing his wife and acquitted on the grounds of temporary insanity.[36] 1991, R v Burgess: Burgess was accused of hitting his girlfriend on the head with a wine bottle and then a video tape recorder. Found not guilty, at Bristol Crown Court, by reason of insane automatism.[37] 1992, R. v. Parks: Parks was accused of killing his mother-in-law and attempting to kill his father-in-law. He was acquitted by the Supreme Court of Canada.[36] 1994, Pennsylvania v. Ricksgers: Ricksgers was accused of killing his wife. He was sentenced to life in prison without parole.[38] 1999, Arizona v. Falater: Falater, of Phoenix, Arizona, was accused of killing his wife. The court concluded that the murder was too complex to be committed while sleepwalking. Falater was convicted of first-degree murder and sentenced to life with no possibility of parole.[36] 2001, California v. Reitz: Stephen Reitz killed his lover, Eva Weinfurtner. He told police he had no recollection of the attack but he had "flashbacks" of believing he was in a scuffle with a male intruder. His parents testified in court that he had been a sleepwalker since he was a child but the court did not buy it and convicted Reitz of first-degree murder in 2004. [38] 2008, Brian Thomas was accused of killing his wife while he dreamt she was an intruder, whilst on holiday in West Wales.[39] Thomas was found not guilty.[