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Use of Brain Scanning in Insanity Defence: Critical Essay

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Insanity is commonly defined as the state of being seriously mentally ill. But does that exempt people from punishment for crimes they committed? Insanity pleas are rarely used, and when they are, they have an extremely low success rate. How is one deemed insane? What are the criteria for an insanity plea? These issues have been and continue to be determined by state lawmakers and precedent-setting court cases. One possible outlet for this determination is the use of brain scans. If someone can be deemed as actually insane or not, it can help mentally ill people receive proper care, and in cases where the death penalty is used, perhaps save a life.

Although the insanity plea has been around since the 18th century, actually determining the validity of the plea has only come around in the last hundred years. In 18th-century England, a test called the 'wild beast test' was used to determine insanity. It was named this because it determined if a person had any understanding or memory of their crime, akin to a wild beast. This test, among others, was administered by psychiatrists to have a professional opinion on whether someone is truly insane or not. In 1843, the McNaughton rules were formed after Daniel McNaughton shot and killed the Prime Minister’s secretary but was acquitted because of insanity. Due to the staggering amount of public backlash, parliament came up with a more clearly defined qualification for insanity, saying that there was a presumption of sanity unless the defense proved at the time of committing the act the accused was laboring under such a defect of reason, from a disease of the mind, as not to know the nature and quality of the act he was doing. America has a much more vague standard, with Ronald Reagan saying in 1984 that the defendant is not responsible if he was unable to appreciate the criminality of his conduct. Although the insanity plea was clearly laid out in 1984, the first use of brain scans in an insanity defense wasn’t for another eight years.

The first known use of brain scans as evidence was in 1992, with Herbert Weinstein as the defendant. Weinstein had strangled his wife and then pushed her body out of a window to make her death look like a suicide. Defense attorneys had PET scans that revealed an arachnoid cyst in the frontal-temporal region of Weinstein’s brain, which 'affected his ability to reason' (Rojas-Burke, 13N). Brain scans being considered evidence, in this case, were met with mixed feelings. Some said that the use of PET scans as evidence has no scientific backing, while others, though, said that it was a step forward in the newly coined (at the time) 'neurological defense'. The scans, along with the opinion of a psychiatrist, argued that “Weinstein’s cognitive faculties were so impaired that he lacked the capacity to appreciate the consequences of his actions or know that his actions were wrong” (Rojas-Burke, 13N). Although this was a breakthrough case for the use of brain scans, Weinstein ended up pleading guilty to manslaughter for a reduced sentence. Daniel Martell, a forensic psychologist, testified in Weinstein’s case and then opened a consulting business called Forensic Neuroscience because he was in such high demand. Martell has been involved in hundreds of criminal and civil cases, as part of both the defense and the prosecution. Though he remains skeptical of the worth of brain scans, Martell doesn’t deny how they have revolutionized the law.

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Modern neuroscience has changed the minds of juries so that criminals receive life in prison instead of death. Brain scans also could have helped John Hinckley Jr., the man who attempted to assassinate President Reagan. Criminal evidence has come a long way to include brain scans, evidenced by the development of the insanity defense throughout history and cases where brain scans have been used as evidence. But negatives include the cost, the time added to a trial, and the fact that it could be considered a rights infringement. Although brain scans are helpful, they can increase the costs of an already expensive trial. A normal trial can cost anywhere from $100 to $400 an hour for a criminal defense lawyer. With cases being 4 or 5 days, and some taking up to 6 months, the legal fees can range from a few thousand to a few hundred thousand. Add on the few thousand dollars that a brain scan costs, which ranges from $1000 to $5000, depending on where you live, the debt could be crippling to some lower-income families. Though some of the cost might be covered by insurance, a large sum is still owed. If the judge or jury declares that a brain scan is necessary, it adds time to what might already be a lengthy trial. Trials can take anywhere from a few days to a few months, depending on the severity of the case. The trial is most likely severe and therefore has been going on for a while if a brain scan has been deemed necessary. In the case of Herbert Weinstein, the case lasted four months before a verdict was reached. Although brain scans probably take less time when the subject is in police custody, it can still take anywhere from a few hours to a few days to determine if the subject is actually insane or not. This also does not account for any surprises that may pop up when the brain scans are inspected. There is also the possibility of court-ordered brain scans being considered a rights infringement. In 2013, a Maryland court ruled in favor of DNA collection upon arrest, saying that it was of 'legitimate government interest' because it could help determine the criminal history of the individual. There is justifiable concern that this could be broadened to include brain scans. Similar to DNA collection being used to determine past criminal history, brain scans could be used to predict future criminal activity. This could result in discriminatory treatment of an individual. This crime prediction fueled discrimination could take the form of being denied housing, insurance, or even employment.

Concerns over the cost, length of the trial, and debate over whether or not a brain scan is a rights infringement are pertinent. Although those concerns are valid, they are outweighed by the positives, such as how brain scans can help people who are actually ill receive proper care, prevent the death penalty from being carried out, and determine if jurors are biased. Using brain scans to determine if someone is actually insane or not helps people who are actually mentally ill receive proper care. Per a 2000 estimation, the National Institute of Mental Health said that 42 percent of people with 'severe mental illnesses' go untreated. Harvard Health also says that an extremely small portion of those actually commit crimes. This contributes to the small percentage of people who claim insanity in criminal cases. Of those people who do claim insanity, using brain scans to validate the claim weeds out the people who aren’t actually ill, as well as getting people who are actually ill the care that they need instead of sending them to prison where they will be worse off. If the death penalty is on the table as a possible punishment, determining if a person is actually insane can save a life. In 40 years, 8,466 people were sentenced to death. Of those 8,466 people, 4,338 are either still on death row or have been executed. Insane people are not at all responsible for the crimes they’ve committed, whether it be because they can’t remember committing it or because they can’t fully appreciate the consequences of their actions. If they die, it is killing a technically innocent man, whether he committed the crime or not. Using brain scans can determine if a person is responsible or not and can help people who are coming to justice, and those who are not, not to be punished. Brain scans can also determine bias in jurors, making for a more fair jury to determine guilt or not. Bias in jurors hinders true justice, and eliminating that bias comes in the form of finding jurors that are unbiased toward the specific case. Eliminating such bias can come in the form of using brain scans on potential jurors. Certain parts of the brain light up when someone recognizes a person or something that they have heard. This can be used to see if someone has seen or heard of the case before and therefore has already determined what they think the verdict should be. This poses an issue because the juror hasn’t heard all the evidence in the case.

Brain scans can be positive or negative depending on how the information gathered is used. The positives of finding proper care and treatment of mentally ill individuals, saving convicted criminals from the death penalty, and eliminating juror bias outweigh the negatives of rights infringement, trial costs, and trial length. The scope of brain scan usage will be a contentious issue as the legal system continues to be inundated with trials and criminal sentencing. This issue will be interesting to watch as lawyers and judges will decide this very important issue with precedent-setting cases in each state.

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Use of Brain Scanning in Insanity Defence: Critical Essay. (2023, November 15). Edubirdie. Retrieved March 1, 2024, from
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