Written by Dr. Nicole M. Vienna

December 28, 2021

If a defendant’s mental health affects their way of thinking or behaving during a trial, the judge, prosecutor, or defense attorney can seek competency to stand trial assessment. Competency to stand trial is when a defendant understands the nature of the legal proceedings against them and would be mentally competent in assisting their legal counsel regarding the case at hand. A person who is not competent to proceed may not be able to stand trial for an alleged crime due to their mental disorder or defect and its impact on their decision making or ability to comprehend what is happening in the legal proceedings. It would be a violation of their due process rights. Ultimately, competency to stand trial is determined by the judge after a review of expert mental health reports and evidence.

Nevertheless, in order to use the insanity defense for a case, the defendant must plead not guilty for a crime because of their mental illness, thus lacking culpability. Defendants using the insanity defense must suffer from a mental illness. In addition, the defendant has to prove to the court that because of their mental illness or defect, they did not understand what they have done, did not know what is right or wrong, and acted upon outside factors. This is established by the defendant as they apply the insanity defense into their case.

The Similarities Between The Competency to Stand Trial and The Insanity.

For example, in the aftermath of both of these rulings, the defendant must be sent to a mental health treatment facility or state hospital to receive treatment in order to stabilize their condition. In addition, to prove these defenses, the defendant must undergo an evaluation to assess their competency or sanity.

There are many differences between competency and insanity in court trials. Below, the differences are listed and explained in depth.

(1) Legal Definition

Competency in court refers to whether or not the defendant will participate at trial and comprehend the legal proceedings. A person’s mental state is evaluated at the time of the assessment.

On the other hand, to be declared legally insane in court implies whether or not the defendant is responsible or has culpability for their crimes due to their mental illness. The person’s mental state at the time of the crime is assessed.
Hence, a large difference between competency and sanity elucidates how competency relates to their mental state at the time of the evaluation and its impact on their ability to take part and be present in court proceedings. In contrast, sanity focuses on their mental state at the time of the crime, which is the defense their attorney will present during the trial.

(2) Term Usage relating to the Defendant

Competency refers to the defendant’s present state of mind as they undergo the legal processing of their criminal case. This can be prevalent when the defendant has trouble understanding their attorney’s role in the legal proceedings or has difficulty rationally assisting their legal counsel in helping in their defense on the case.

Nevertheless, insanity is associated with the defendant’s state of mind during the crime was committed. The defendant’s mental illness may corrode with their state of mind as they enact the crime. While their mental state may be intact during their sanity evaluation, it is not relevant to their status at the time of the crime.

(3) Criteria

To qualify for competency to stand trial, an individual must:

  • Have a basic understanding of the criminal proceedings
  • Be able to assist counsel in the conduct of a defense in a rational manner.

To determine the insanity defense in a trial, a defendant must enter a plea of Not Guilty by Reason of Insanity (NGRI). To qualify for legal insanity, it requires that the defendant with a mental disorder is incapable of:

  • Knowing the nature of their actions or;
  • Understand the nature of their actions or;
  • Distinguish between right or wrong at the time of the crime was committed

These particular criteria are important to consider because if the defendant does not meet any of these requirements, then they are presumed to be sane during the crime or trial. Thus, the defendant’s case will continue as someone who is mentally competent or sane.

(4) Court Rulings

There are a variety of court rulings that relate to competency to stand trial and the insanity defense.

The court rulings related to competency to stand trial includes:

  • Dusky Standard: A criminal defendant is ruled as incompetent if, because of a mental illness or defect, they DO NOT understand the nature of the court proceedings and cannot rationally assist their legal counsel in making decisions. This is the original case (Dusky v. United States) that created this standard or requirement in order to rule out whether or not someone is competent to stand trial.
  • Penal Code 1368: This penal code correlates with the defendant’s mental competency to stand trial. In this case, the judge believes that the defendant may not be mentally competent enough to go through a trial. Therefore, the defendant will undergo a competency assessment from a qualified expert.

Furthermore, the court rulings relevant to the insanity defense constitutes with:

  • M’Naghten Rule: A criminal defendant is not guilty by reason of insanity. This case focuses on whether the defendant knew the nature of the crime and/or if they understood what was right or wrong during the time they committed the crime. This ruling relates to the insanity defense because it tests the defendant’s sanity and rules out their culpability because of a mental illness or defect.
  • Penal Code 1026: This penal code explains that if a defendant moves forward with a plea of not guilty by reason of insanity or if a jury finds the defendant guilty, the question of whether the defendant was legally sane or insane at the time the offense was committed shall be promptly evaluated and presented in a hearing either before the same jury or before a new jury. The discretion is up to the court. The jury will then be tasked with returning a verdict deciding if the defendant was sane at the time the offense was committed or was insane at the time the offense was committed.

(5) Aftermath of Decisions

When the defendant is declared legally incompetent to stand in the trial, the trial itself is suspended. The defendant will be sent to the Department of State Hospitals or a facility where they will receive proper treatment for their mental illness. The treatments are meant to stabilize the individual’s condition until they are competent enough to return to trial, depending on the progression of their treatment.

Alternatively, when the defendant is declared legally insane, their trial outcome will typically receive the same sentence as someone who was “guilty,” but the defendant is supposed to start their sentence in a mental health facility and might be transferred to prison after treatment is completed. Alternatively, they could spend the sentence in a state hospital under professional treatment. Therefore, the defendant would be sentenced to a psychiatric hospital rather than prison due to their mental illness or defect.


Although there may be some similarities between competency and insanity, there is a prominent difference that should be considered when approached with these types of cases. For example, competency relates to whether or not the defendant can comprehend and understand what is going on in the legal process and their role in the case. On the other hand, insanity corresponds with how the mental state of a defendant affected their way of thinking when they committed the crime.

If you would like to schedule a consultation with Dr. Vienna to learn more about competency to stand trial and not guilty by reason of insanity, contact our office at (626) 709-3494. 

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