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What’s the difference between the insanity plea and incompetency?

What's the difference between the insanity plea and incompetency?

The terms sanity and competency are heard so often in media coverage of high-profile criminal trials that it can be easy to confuse the two. A lot of people may wonder how it is possible for somebody to enter an insanity plea when they have already been deemed fit to stand trial. While sanity and competency are related in some ways, in the justice system these are two very separate and different legal concepts. Nonetheless, they are both very important for understanding how the justice system works and they have an immense impact on both how cases are tried and how sentences are handed down. Here is a look at some of the differences between the insanity plea and the competency to stand trial.

Understanding the charges

For anybody to have a fair trial he or she must be able to understand the charges against him or her. This basic principle is where the concept of competency to stand trial comes from. A defendant must be able to understand what they are being charged with and must be able to discuss the charges with his or her attorney in a reasonably rational way in order to be considered competent to stand trial. In other words, the competency of the defendant is determined before the trial even begins. Being declared competent to stand trial simply means that the defendant understands the charges against him or her. It is not a statement about whether or not that defendant was sane or insane when he or she allegedly committed the offense that is being tried. Competency to stand trial merely concerns the defendant’s state of mind and mental abilities during the trial itself. Furthermore, competency to stand trial is guaranteed by the U.S. Constitution, which guarantees the right to due process for those accused of a crime.

State of mind when the crime was committed

In contrast, the insanity plea concerns the state of mind of the defendant when the alleged crime was committed. When determining whether or not a defendant is insane, the court is not considering the defendant’s state of mind during the trial, but rather during the criminal act. So a person can be found to have been legally insane when a crime was committed, but nonetheless competent to stand trial later on. In fact, a person can only be successfully found legally insane so long as they are competent to stand trial since being incompetent to stand trial means no trial can take place. In other words, a defendant can be both legally insane and competent to stand trial, but not incompetent to stand trial and legally insane. This distinction is one that often confuses people who are not familiar with the justice system since they wrongly assume competency to stand trial is a judgment on the defendant’s general state of mind, including when the alleged crime was committed. Furthermore, unlike competency to stand trial, insanity laws are not determined by federal law but rather by state laws. This means that not all states have to consider whether or not a defendant was insane when he or she allegedly committed an offense.

insanity plea

How insanity can still lead to a guilty verdict

It is not enough that a defendant merely is shown to have been insane when he or she committed the offense in question. Rather, it must be shown that the defendant’s insanity made it impossible for him or her to understand that the offense being committed was illegal. For example, a man may have hallucinations about aliens living in his home. If he finds out that his wife has been having an affair and, in anger, murders her, then he would still most likely be found guilty of murder (so long as there was enough evidence against him) since his hallucinations did not deter him from the fact that he knew that murdering his wife was illegal. Of course, the man could only be found guilty of the crime if he was also declared competent to stand trial.

However, if that same man believed that his wife was an alien and was trying to murder him, then his state of mind would have made it impossible for him to understand that committing violence against her was wrong. Rather, he may have seriously believed that violence was necessary for protecting his own safety, thus making it impossible for him to be responsible for his actions.

How competency is determined

Competency and insanity are determined by different methods. The standard for determining whether an individual is competent to stand trial is, in fact, a very low one, whereas the standard for proving that a defendant was insane when an offense was committed is usually a high one. To be proven competent to stand trial, the defendant need only understand the charges against him or her and be able to converse with an attorney in a relatively reasonable manner. Competency does not mean that the defendant needs to have a deep understanding of the:

  • Charges
  • Legal Technicalities
  • How the court system works

In practice, the low standard for proving competency means that only those who are extremely mentally unwell can be found incompetent to stand trial. There is a very good reason for setting such a low standard for competency: it ensures that more people are given the chance to have their case heard in court.

How insanity is determined

Because the insanity plea is determined by state laws, each state has its own rules for determining whether or not a defendant was legally insane when he or she committed the offense in question. Generally, however, states that allow the insanity defense can be divided into two groups: those using the M’Naughten rule and those using the Standard Model.

Currently, there are 26 states that use the M’Naughten rule. The M’Naughten rule is named after the defendant in an 1843 British case, Daniel M’Naughten, who had tried to assassinate the British Prime Minister and who was considered insane when he tried to do so. The M’Naughten rule was established by that case and it essentially states that to be considered insane the defendant must have suffered from a mental illness that made it impossible for him or her to understand the nature of the act he or she was committing or, even if he or she knew what she was doing, could not have known that the act was wrong. Some states have also modified the M’Naughten rule to allow for the insanity defense if the defendant suffered from an “irresistible impulse” that forced him or her to commit a crime even if he or she knew that the offense was wrong at the time.

In contrast, 22 states along with the District of Columbia use the Model Standard, which was laid out by the American Law Institute in 1962. The Model Standard is generally seen as a less restrictive standard than the M’Naughten rule. It requires that the defendant lack “substantial capacity” to either understand that his conduct was criminal or to otherwise act in a way that was compliant with the law.

Furthermore, three states do not allow the insanity defense at all. These states are Idaho, Montana, and Utah. In these states, a defendant cannot plead not guilty because of insanity. However, a defendant can still be found guilty but insane, which may result in that individual being committed to a psychiatric institution instead of or in addition to prison. In these states, the accused must still be found competent to stand trial.

 the difference between the insanity plea and incompetency

Judge vs. Jury

The decision about whether a defendant is incompetent and/or insane also differs depending on what matter is being decided upon. A person’s competency to stand trial is, for example, determined by the judge. A defendant’s insanity, meanwhile, is determined by the jury when it renders its verdict. Again, competency is determined at the beginning of the trial, while insanity is determined at the end during the verdict. Hopefully, of course, the jury will take into account the opinions of psychiatrists and/or psychologists who act as expert witnesses during the trial when determining whether or not an individual was legally insane when the crime was committed.

What about guilty but mentally ill?

Many states also have laws that allow courts to reach a verdict of “guilty but mentally ill” (GBMI). The GBMI verdict means that the defendant receives the same sentence as somebody who was simply found guilty for the same crime but was not suffering from a mental illness. In a GBMI verdict, the court will often sentence the defendant to a prison sentence but will also require that individual to receive treatment for his or her mental illness. Even if that individual is cured of his or her mental illness, he or she will still have to serve out the rest of the sentence in prison. The GBMI verdict is highly controversial, with supporters saying it ensures that those who have committed crimes are held accountable for their actions while critics contend the verdict absolves the court of determining whether or not the defendant was actually responsible for his or her actions.

The Four Tests Used for Determining Legal Insanity

What happens after being found incompetent?

A person who is found incompetent to stand trial will usually have their trial delayed until such a time when he or she is deemed to have regained his or her mental competence. Essentially, this means that the defendant will receive treatment until they have sufficiently recovered from their mental health problems. However, an individual’s trial cannot be delayed indefinitely–rather, the delay must be deemed reasonable. Delaying a trial indefinitely is a violation of one’s constitutional rights, most notably the right to a speedy trial. The Supreme Court held that a trial in such cases cannot be delayed for longer than is necessary in a landmark 1972 case. However, even if the defendant never regains his or her sanity, that person can nonetheless be forcibly committed to a mental institution, especially if that person is deemed to pose a threat to the safety of themselves or others.

What happens after being found criminally insane?

A person who is acquitted by reason of insanity, on the other hand, will usually be committed to a mental institution. The conditions of their release back into society if they recover from their mental illness vary from state to state. In some states, for example, the individual will first have to complete a commitment hearing to determine whether or not he or she needs to be committed to a psychiatric institution. In other states, however, commitment to an institution is automatic upon a verdict of insanity. In some cases, the individual may be released back into society relatively quickly if that person is determined to no longer pose a risk to themselves or others. However, in many cases, especially in cases involving murder or attempted murder, the standard for release will be set much higher.

While many laypeople may think that being found “not guilty” for an offense that an individual clearly committed is unfair, it is important to keep in mind that those declared insane are not automatically released back into society. In fact, studies have shown that those found not guilty by reason of insanity spend as much time on average confined to a psychiatric institution as those who are found guilty of the same types of crimes spend incarcerated in prison. Furthermore, even after release, the individual may be required to take steps to ensure they no longer pose a risk, such as by taking medication, visiting a doctor, or complying with other instructions.

An insanity plea and a claim of being incompetent to stand trial may sound similar but they are, in fact, very different from one another. As the above article shows, however, both concepts have important implications for ensuring that everybody receives a fair trial. Competency ensures that a defendant understands the offense he or she is being charged with and can discuss those charges in a reasonable manner with an attorney. Insanity, meanwhile, ensures that those who could not have appreciated the criminality of their actions are not unfairly found guilty of committing those actions. Either way, competency and insanity pleas help protect the rights of the accused while also ensuring that public safety is upheld.


This article contains general legal information but does not constitute professional legal advice for your particular situation. The Law Dictionary is not a law firm, and this page does not create an attorney-client or legal adviser relationship. If you have specific questions, please consult a qualified attorney licensed in your jurisdiction.

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