"It wasn't me, sir.  My brain made me do it!"

But wait, isn't your brain....you?  This question has been the subject of endless debate, and the answer really depends on your own personal philosophic beliefs.  However, from a purely objective point of view, you are.  Basically, you're a genetically unique bag of water that manages to think and feel because of billions of tiny cells called neurons...and a conscience.

To have a "conscience" is to have the ability to discern between right and wrong.  Whether this moral compass is innate hardware or externally installed by society, it is commonly accepted as a defining trait of humanity.  What separates us from "the rest" is our ability to weigh consequences and make decisions.  In some cases; however, this ability may be inhibited or altogether nonexistent.  In these situations, the person would be unable to recognize the seriousness of their actions, or even--in extreme circumstances--that they even committed the act at all.  To account for occasions such as these, our legal system has adopted the Insanity Defense as a way to deal with those who are mentally unstable.

The sentiment that the mentally ill should be spared from severe consequences was first documented in Ancient Greece, over 2,000 years ago.  The great philosopher Plato once noted that, "someone who may commit an act when mad or afflicted with disease...let him pay simply for the damage; and let him be exempt from other punishment."  Other notable figures have echoed this belief throughout history, such as Marcus Aurelius' statement that "madness is its own sole punishment," or Shakespeare in his Hamlet, where he wrote, "If I wrong someone when not myself, then Hamlet does it not, Hamlet denies it.  Who does it then?  His madness."

So who is the culprit: the Man, or his Madness?

The definition of "madness" has evolved over the ages: from King Edward II's decree that a man should be considered insane if his intelligence was that of a "wild beast," to the much stricter and controversial diagnoses today.  One of the most defining cases in the history of the defense was the trial of Daniel M'Naghten in 1843, where a psychotic Scotsman was ruled insane following his attempted shooting of the English Prime Minister, Sir Robert Peel.  This case established a legal definition of insanity known as the M'Naghten Rule.  The rule states,

"That if the accused was conscious that the act was one which he ought not to do; and if the act was at the same time contrary to law, he is punishable. In all cases of this kind the jurors ought to be told that every man is presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary be proved to their satisfaction: and that to establish a defence on the ground of insanity, it must be clearly proved that at the time of committing the act the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing, or as not to know that what he was doing was wrong."

This standard--although still presently in use--has for the most part given way to the definition put forth by the American Law Institute, which is composed of two main rules: that of the cognitive and the volitional.  The cognitive rule, echoing the M'Naghten standard, says that the perpetrator is to be considered insane at the time of a crime if he was not aware that what he was doing was wrong.  The volitional rule presumes the existence of free will, and says that a person is insane when not in voluntary control of their actions.

The volitional rule is what causes most of the controversy associated with the Insanity Defense, as it raises the question of true responsibility.  Should a person be held accountable for what he is by nature?

Before the recent advances in neuroscience and technology, the only way to discover the biological differences in psychotic criminals and sane persons was by means of autopsy--and, obviously--that is far too late to pardon the execution of an insane convict.  For example, after the autopsy of the "Texas Sniper," Charles Whitman, it was revealed that he had a brain tumor in his limbic system (specifically on the hypothalamus), an area of the brain associated with the control of aggression.  Whitman was killed at the scene of his massacre, but if he had gone to trial, he may have cited the volitional rule as his defense.  Previous to the murders, he wrote in his suicide note that he felt subject to "overwhelmingly violent impulses."  Another, perhaps more famous example of a biological impairment is the case of Dan White, who murdered San Francisco mayor George Moscone and city supervisor Harvey Milk.

This case is the source of the famous "twinkie defense," where White's lawyer claimed that the popular junk food had raised his blood-sugar to a dangerous level, causing White to lose voluntary control over his actions.  Although this is not an anomaly that occurred naturally, it still could have potentially affected his behavior, making him temporarily insane.  This evidence was enough to lessen the potential severity of the decision, as White was sentenced to only seven years for manslaughter.

Now while in some instances these biological impairments have been proven to affect the sanity of individuals, this is not always the case, because the biology isn't the only factor.  You can't say that 100% percent of people with a certain brain structure are psychopaths.  While an anatomical anomaly may predispose someone to behave a certain way, there are still other factors that can prevent--and trigger--criminal actions.  For example, researchers that study the criminal mind using brain scans have found that most psychopaths share a common physical malformation: the orbitofrontal cortex is dysfunctional.  This region of the brain is believed by many scientists to control ethical decision-making and the inhibition of impulses.  Damage to this area may lead to uninhibited bouts of rage and violence.

Hypothetically, if a psychopath could be considered the product of a certain mixture of nature and nurture, this structural difference would be but one key component of the "recipe" for a psychopath.  Alone, these ingredients could cause vastly different outcomes, but together in one person, they point towards a singular probability: psychopathy.

The second ingredient would be genetics, the inherited traits passed down through the generations.  A genetic predisposition to violence would provide solid evidence that a criminal may be a psychopath, and can you really punish someone for the behaviors of their ancestors?  Certain genes still persist today that used to benefit humans in circumstances far different from our modern world.  For instance, consider the monoamine oxidase-A gene (simplified to MAO-A).  Dubbed the "Warrior Gene," this gene is responsible for the regulation of serotonin in the brain.  Serotonin is a neurotransmitter that regulates mood, so if a person were to inherit the high-aggression variant of MAO-A, his ability to calm down would be affected, leaving the anger to build unchecked by the body's natural calming agent.

The third and most crucial element of the recipe is the nurture component.  Say that a child with a dysfunctional orbitofrontal cortex was born into a family that was historically associated with some very shady, violent characters....but was put up for adoption.  This child was then lucky enough to be adopted by loving parents, who showered the infant with affection and gave him innumerable opportunities to play with other kind, sociable children.  Now, would you still expect this child to grow up to be the emotionally void sociopath that his genes "destined" him to be?  James Fallon, a neuroscientist employed by the University of California at Irvine, would emphatically reply, "No."

Fallon, a researcher who studies the criminal brain, discovered that his own family had a rather violent past, and decided to see if his own brain passed the "psychopath" test.  To his surprise, it did.  He was shocked at first, but later he jokingly commented, "You see that? I'm 100 percent. I have the pattern, the risky pattern...In a sense, I'm a born killer."  Luckily for him; however, he had a wonderful childhood.  As for the others who weren't as fortunate and suffered the childhood abuse that triggers their own violent tendencies, Fallon says, "It's an unlucky day when all of these three things come together in a bad way, and I think one has to empathize with what happened to them."

 

*Author's Note: This is where the factual history and the scientific research ends and the risky business of personal opinion begins to take over.  Some may argue for or against the abolition of the insanity defense, and also may have strong feelings regarding the ethics of purposely keeping "guiltless" people apart from society.  Feel free to voice your disagreements in the comments section below.*

So should a genetic predisposition to violence be enough to lessen the severity of a sentencing?  In some cases, yes, but otherwise it should not.  There are many factors to consider when you must determine the sanity of a person.  Fortunately the Insanity Defense is not widely abused, it is only plead in roughly 1% of all criminal trials.   The defense is a valuable tool in the courtroom, for it can provide protection for those who truly need it, but it should be used with caution and careful consideration.  The application of neuroscience in the courtroom should not mean the end of all responsibility, it should be used as an aid, not a shield.

 

Sources:
"A Neuroscientist Uncovers A Dark Secret," by Barbara Bradley Hagerty, NPR
Should We Retain the Insanity Defense? -Author Unknown