Continuing this week is the documentary series that delves inside the minds of killers in an attempt to find out why they kill; how they get away with their crimes; and how they rationalise their actions.

In each programme, Dr Michael Stone, a forensic psychiatrist at New York City’s Columbia University, considers killers and places them on his ‘most evil’ scale. In this edition, Stone focuses on serial killers who have suffered from extreme delusions and schizophrenia – including a man who believed he could prevent earthquakes through the act of murder, and a woman who believed she was being stalked by an imaginary nemesis who worked for the Nazis.

Many killers have acted on irrational impulses and paranoid beliefs often triggered by psychotic episodes. One such killer was Herbert Mullin who murdered 13 people in a four-month killing spree in the early 70s. Mullin believed that he was hearing voices commanding him to kill – including that of his father – and that his actions would prevent earthquakes. He enjoyed a stable, healthy childhood and showed great promise as a student before a tragic event when he was 18 changed the course of his life. His best friend was killed in a car crash, which saw Mullin spiral into paranoid beliefs and delusional behavior. “It is not uncommon for the stress of a traumatic event to aggravate a predisposition to mental illness and bring about symptoms that are yet to emerge,” notes Stone.

Mullin became a political malcontent in the late 60s, registering as a conscientious objector to the Vietnam war and experimenting with hallucinogens. In the early 1970s he turned against his earlier convictions and began to formulate an irrational philosophy based on telepathic messages he was receiving. He drew the conclusion that he could prevent earthquakes via murder. Among his victims were a homeless man, a priest and four teenage campers. After being rejected by the marines for service in Vietnam due to earlier drug offences, he killed the friend who had sold him the hallucinogens years earlier. Mullin was eventually arrested in 1973 and is still serving life imprisonment.

Neurological studies suggest that sufferers of schizophrenia can lose up to 25 per cent of brain tissue, robbing them of the ability to distinguish between real and imaginary voices. Stone believes the delusional nature of Mullin’s illness contributed greatly to his deeds, so only places him at 13 on his scale of evil.

Stone’s second case study tonight is that of Diana Dial, a middle-aged mother of two who murdered her flatmate, believing him to have poisned her. After a normal childhood and a healthy marriage, Dial’s life fell apart after she suffered a miscarriage in 1979. “The intense pain [she] experienced may have brought about a psychotic episode that developed into a mental illness,” remarks Stone. Her husband left her after she became “anxious and irrational”, believing she was being stalked by Nazis and, in particular, a shadowy foe named Cheryl Thompson, who was hellbent on ruining Dial’s life. She was diagnosed with schizophrenia but neglected to take her medication, considering herself to be perfectly sane.

Dial’s delusional behaviour reached its apex in 1997 when she shot dead her flatmate Jack Ferris, believing him to have poisoned her. Fearing for the safety of her children, she felt she had no choice. Stone visits Dial in prison where she is serving a 60 years-to-life sentence, and is shocked by her articulate assertions that her suspicions were far from imaginary. “[Ferris] was offered a billion dollars to poison people that Cheryl Thompson and her dad didn’t like,” maintains Dial. Stone, taking into account Dial’s medical condition, judges her to be at seven on his scale of evil.

Also in this episode, Stone examines the case of insurance salesman Eric Bieshline, a psychopath whose condition was exacerbated by heavy drug abuse. Bieshline murdered a number of elderly victims before being jailed in 1994.

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