The legal system assumes that people can explain their actions. If a case goes to court, the accused is expected to explain their actions, and if it turns out that the person acted unconsciously, their guilt is usually reduced. While this opens space for manipulation by lawyers, judges have to understand the nature of madness.
Scientists William Hirstein and Katrina Sifferd decided to find out how the courts understand "guilt."
When it comes to establishing the defendant's mental state, experts are focusing on the processes in the prefrontal cortex - the area that controls other, less complex cognitive processes. The main processes include attention, memory, decision making, planning and self-control. All of them are activated when the brain needs to develop a new model of behavior in response to a new task. The Court shall determine the degree of guilt of the defendant based on whether the executive functions of the brain are intact, that is, the work of dorsolateral and ventrolateral frontal lobes, and the medial prefrontal and orbitofrontal lobe.
Take, for example, a strategy to protect sleepwalking killers. While person is asleep, the activity of motor cortex is suppressed. In case of a sleep disorder called parasomnia, the activity of this area is not fully suppressed, so people can move freely, as if they were awake. The most difficult case of parasomnia is sleepwalking - sleepwalkers can talk, cook, and even drive a car while sleeping. The task of a lawyer in this case is to prove that their client was sleeping at the time of the crime, therefore, legally could not be considered guilty.
The first case of successful use of this strategy was the case of Kenneth Parks. In May of 1987, 23-year-old Parks, who was in distress due to severe financial problems, arrived at the house of his wife's parents and brutally murdered them. After that, the young man went to the police and said that he killed someone. When Parks' case was sent to court, medics confirmed that the accused was a sleepwalker, and at the time of the murder he was asleep. Since the description provided by Parks was in full compliance with the testimony of the expert, the court acquitted him of all charges.
To date, scientists have evidence that the acts committed while sleeping are not controlled by the prefrontal cortex of the brain. They are controlled by other areas of gray matter, which explains why people are still able to act. The court, when determining guilt, evaluates only the executive functions of the brain. In the case of Parks the decision was quite difficult. He had a criminal record for theft, and had a motive for murder. However, the fact that the executive functions of his brain at the time of the murder were disabled, the court acquitted him.
Mental disorders that are not characterized by impaired executive function are usually not sufficient to justify crimes. This is the case of psychopaths - people unable to experience strong emotions and empathy for others. However, in recent years, their defenders started introducing magnetic resonance imaging and positron emission tomography to prove that their clients are experiencing cognitive deficits - like juveniles and mentally retarded whom the court usually recognizes as people with executive dysfunction.
The trial of Brian Dugan was one of the first cases in which the defendant used his psychopathy as a mitigating circumstance. In 1983, Dugan was charged with kidnapping, rape and murder of a ten-year-old girl. Neuroscientist Kent Kiel presented evidence to the court that Dugan had impaired brain - of 40 classic signs of psychotic he had 37. The volume of his brain was smaller than that of an average person, which was used by the defense. The court, however, sentenced the murderer to death. While psychopaths suffer from cognitive deficits and do not understand the value of human life, it is not the disorder that can mitigate the court sentence.