Despite the popular perception that those who kill must be insane, it is pretty rare for a killer to actually mount a successful insanity defense. A plea of not guilty by reason of insanity is an admission of committing the crime in question, but a request that they cannot be held criminally responsible for committing the crime because of an altered state of mind at the time.  If it is deemed that an individual is not of their right mind at the time of committing the crime, they are not legally guilty.

In the US, less than one-percent of criminal cases use the insanity defense but that has not stopped plenty of killers claiming their horrific actions were due to mental illness. The McNaughton rule is a method most commonly used to define whether a defendant is insane and is based on whether or not the person in question knows the different between right and wrong at the time the crime was committed.  When a plea of insanity is entered, both the prosecution and the defense bring in their own psychiatrists to assess the defendant to come to their own independent conclusions as to the mental health status of the defendant and any formal diagnosis which should be given.

Some on this list are famous American cases. Some went to trial with an insanity defense and rightly so with evidence of mental illness being the driving force behind their crimes. Others, however, saw the defense of insanity as a get out clause to side step responsibility for taking the life of another.

Kenneth Bianchi

Kenneth BianchiOne half of the ‘Hillside Stranglers’, Kenneth Bianchi confessed to rapes and murders which he carried out with his cousin Angelo Buono, but he came up with a far-fetched story in his own defense. Bianchi claimed he was suffering from Multiple Personality Disorder, now officially known as Dissociative Identity Disorder and it was one of his ‘alters’ —  his other personalities which he had no control over — who had committed the murders.

He was soon called out as faking his mental illness with a forensic psychiatric report citing too many inconsistencies in his tale which did not match what is known about the disorder and how it manifests. As a result, Bianchi retreated, withdrew his plea of insanity, and opted to plead guilty to all charges instead. Furthermore, he accepted a plea deal where in exchange for giving evidence against his cousin, he would avoid the death penalty. In a long and drawn out trial spanning two years, Bianchi pleaded guilty to five murder charges and received a life sentence which he is serving in Washington.  His cousin, Angelo Buono, was convicted of nine murder charges and died in prison in 2002.

Ted Bundy

Ted BundyBy January 1980, serial killer Ted Bundy had already been tried twice for his succession of heinous crimes against women. In February 1976 he was found guilty of the aggravated kidnapping of 18-year-old Carol DaRonch in Salt Lake City, Utah and received a sentence of up to 15 years in prison. Charged with the murder of Caryn Campbell eight months later, Bundy escaped from police custody and carried out a brutal attack at Florida State University on 14 January 1978, attacking four young girls and killing two.

Just one month later, while still on the run, he kidnapped, raped and murdered 12-year-old Kimberly Leach.  Finally arrested six days later, Bundy found himself on trial again.  In his second trial in June of 1979 in Miami, Florida for the attack at the University sorority house, Bundy represented himself protesting his innocence and pleading not guilty but was unanimously found guilty and given the death penalty.  In his final trial in January 1980 for the murder of Kimberly Leach, despite his previous convictions and death sentence, Bundy decided to let a defense team take control and pleaded not guilty by reason of insanity. Quite probably the only defense option he had left to try.

With little to no evidence to support his plea, the jury found him guilty and a second death penalty was handed down.  In the period before he was executed, Ted Bundy confessed to at least 30 other murders of young women. He was executed in the electric chair at Starke State prison in Florida on 24 January 1989.

Jeffrey Dahmer

Jeffrey DahmerBetween 1978 and 1991 Jeffrey Dahmer murdered seventeen young men in Milwaukee, Wisconsin. Luring his victims back to his home after meeting them in gay bars, Dahmer would ply them with drink and strangle them when they were least expecting it. He then went on to mutilate their bodies, engage in cannibalism, and sexual abuse of the corpses before keeping their body parts around his apartment. When caught he openly confessed to his crimes, saying he wanted to understand why he did it.  Accessed by numerous psychiatrists, Dahmer was diagnosed with Borderline Personality Disorder.

Over a two-week trial in 1994, Dahmer’s defense entered a plea of not guilty by reason of insanity citing his mental health as the cause of his disturbed behaviour and that he was unable to control himself. The prosecution in rebuttal called Dahmer a calculating killer who purposely and willfully covered up his crimes so he could continue killing. Expert witnesses on both sides argued about Dahmer’s state of mind and his motivations. In a case where many expected the insanity plea to hold, it was rejected by the jury and Dahmer was found guilty of 15 murders and given a life sentence for each. Two years later, Dahmer was murdered in prison by another inmate.

Bruco Eastwood

Bruco EastwoodOn 23 February 2010, 33-year-old Bruco Eastwood opened fire at Deer Creek Middle School in Littleton, Colorado just a few miles from Columbine High School where 13 students were killed in a mass shooting in 1999. Two students were shot before he was tackled to the ground by two courageous teachers. In July 2011 Eastwood pleaded not guilty by insanity as his case went to trial.  An extensive history of mental illness was presented with evidence Eastwood had been hearing voices and suffering hallucinations from as early as 2002.

He was diagnosed with schizophrenia, an illness his defense explained featured delusions, hallucinations, and internal voices which drove Eastwood’s behaviour. A total of three forensic psychiatrists gave their opinion that Eastwood was insane with impaired ability to distinguish right from wrong. After a three-week trial, the jury agreed that Eastwood was suffering from mental illness and not in full control of his actions at the time of the shooting, finding him not guilty by insanity. He was sentenced to the Colorado Mental Health Institute at Pueblo where he remains today.

Albert Fish

Albert FishA name not so well-known, Albert Fish was a horrific serial cannibal who preyed on children in the early 20th century in New York. A man who discovered early in his life he had abnormal feelings towards youngsters, he entered relationships with young men only to kidnap and torture them to carry out his twisted sexual perversions.  Although married for a time and the father of six children, Fish continued his attacks with self-harm also featured in his behaviour.  Fish inserted multiple needles into his abdomen and pelvis and hit himself with planks of wood.

In the years before he was caught Fish would take any opportunity to kidnap a child, inflicting his torture on them before reportedly eating their flesh. In a bizarre rambling letter he sent to the parents of one of his victims, he told them in detail what he had done to their 10-year-old daughter and it was this letter that led to his capture. Albert Fish confessed to that murder and it is believed he may have killed up to nine victims. Fish claimed he heard God’s voice and was instructed to kill. In 1936, however, he was deemed sane and capable of standing trial.  Appalled at his crimes, he was quickly sentenced to death and executed in the electric chair at New York’s Sing Sing Correctional Facility.

Lisa Montgomery

Lisa MontgomeryIn 2004, Lisa Montgomery from Kansas posed as an expectant mother in an online chat room making friends with pregnant Bobbie Jo Stinnett. On 16 December. the two had agreed to meet at Bobbie Jo’s house and upon arrival Montgomery attacked Bobbie Jo, strangling her before cutting her unborn baby out of her womb. Lisa Montgomery was not pregnant and was desperate for a baby, so desperate she was prepared to go to any lengths to have one. Montgomery took the baby home and pretended to everyone, including her husband who had believed her pregnancy story, that the newborn baby was hers.

She was arrested the following day and charged with murder and kidnapping. At her trial in 2007, she mounted a defense of not guilty by insanity with various psychiatrists testifying that she suffered with pseudocyesis delusion and citing sexual abuse as a child and post-traumatic stress disorder as contributing factors.  The prosecution presented its own experts who testified that Montgomery did not suffer with the condition and knew exactly what she was doing when she murdered Bobbie Jo Stinnett and stole her baby. The jury rejected the insanity plea and found Montgomery guilty of murder, sentencing her to death. Lisa Montgomery currently sits on death row in Fort Worth, Texas.

James Holmes

James HolmesFew are not familiar with the name James Holmes after one of the most publicized and debated trials in history took place in 2015. The Colorado movie theater shooting on 20 July 2013 was a mass shooting that claimed the lives of 12 people with over 70 injured. James Holmes attended a midnight showing of The Dark Knight Rises at the Aurora multiplex theater in Colorado only to slip out of a side door soon after the film started, leaving the door ajar. Minutes later Holmes returned, dressed in full protective gear and armed with gas canisters.  After throwing the canisters into the packed theater, he opened fire with three different weapons. After his arrest, Holmes reportedly offered to plead guilty to avoid the death penalty, an offer rejected by the district attorney who wanted the death penalty.

In May 2013, James Holmes pleaded not guilty by insanity to all 165 charges against him including murder and attempted murder.  His defense argued that Holmes was mentally ill and in an episode of psychosis at the time of the shooting, however, the jury found Holmes guilty on all charges.  Unable to reach a unanimous verdict on whether he should receive the death penalty, the judge sentenced James Holmes to life in prison with no possibility of parole. Holmes began his sentence at San Carlos Correctional Facility in Pueblo but was moved to another prison, currently not disclosed, in 2016 after he was attacked by another prisoner.

Steven Steinberg

Sleep-WalkingIn a curious case of sleepwalking murder, Steven Steinberg claimed he was asleep when he killed his wife by stabbing her 26 times at their home in Scottsdale, Arizona in 1981. Although not strictly an insanity defense, murder through sleepwalking has been claimed to be possible due to a temporary state of ‘dissociative reaction’, where the sleepwalker is not consciously aware of their behaviour and therefore cannot be held criminally responsible for it. In Steinberg’s trial, the jury accepted this defense and found him not guilty of murder due to temporary insanity.

As Steinberg was entirely sane and rational at the time of his trial, he was released from custody a free man. Although the jury knew he had murdered his wife, they felt they had to deliver a not guilty verdict on the basis that his sleepwalking state meant that he did not know what he was doing. A similar case appeared in Toronto, Canada in 1987 where a sleepwalking Kenneth Parks left his home and drove 15 miles to his in-laws, where he murdered his mother-in-law and seriously wounded his father-in-law. Parks’ sleepwalking defense was successful, with the jury finding him not guilty of all charges. He too left court a free man.