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Is Mental Illness a Defense in Criminal Cases?

Dealing with mental illness is an extremely personal and private matter, and is often something people would rather not talk about. That said, while most people are reluctant to talk about their mental challenges in other areas of life, it is often used as a defense when someone is accused of committing a crime. 


As part of building a criminal defense, mental health disclosures may be relevant in determining guilt and the appropriate punishment for the accused. If you need advice about any criminal charges brought against you and how mental illness plays a role in your case, consult a Columbia criminal defense attorney right away. 

How Mental Illness is Viewed in South Carolina

Under the South Carolina Code of Law, a defendant’s mental health issues or a claim of insanity is considered an ‘affirmative defense.’ This means that the criminal defense attorney will argue that their client should be found not guilty, even if the prosecution can prove beyond a reasonable doubt that the defendant committed the crime he is being charged with. 


In these cases, criminal defense lawyers are important to have on your side. The attorney will have to prove that the defendant lacked the mental capacity to distinguish between what was right or wrong–legally or morally–when the crime was committed. 

How Mental Illness Can Be Used as a Defense

Mental illness can be used as a defense in one of three ways:


  • Competency to stand trial: If the defendant’s mental illness prevents them from assisting in their own defense or understanding the charges against them, they may be held incompetent to stand trial. This is determined by a court-ordered evaluation performed by the Department of Mental Health. 


  • Capacity to conform: If the defendant’s mental illness is such that they could not distinguish between right and wrong when committing the crime, this can be used as a legal defense. An example would be someone with schizophrenia who was hallucinating when committing an assault. An individual’s capacity to conform is also determined by a court-ordered evaluation performed by the Department of Mental Health. 


  • Mitigation: If the defendant’s mental illness is not at the level necessary to establish an inability to participate in their defense or to understand right from wrong, it may still be used during mitigation. This means the defense attorney can negotiate with the prosecutor to reduce charges or settle for a lowered or probationary sentence because of mental issues.

What Happens if You File an Insanity Plea

When an insanity defense is used in criminal matters, there are several potential outcomes:


  • The defendant may be found not guilty by reason of insanity. 
  • The defendant may be found guilty but mentally ill. 
  • The defendant may be found either guilty or not guilty based on the majority of evidence. 


For an insanity plea to be successful, the defense must convince the jury that the defendant’s mental illness prevented them from knowing right or wrong. Simply showing that the mental illness interfered with the defendant’s impulse control is insufficient for a not-guilty verdict. It is also always possible the jury will still convict the defendant, even if they have been made aware of the defendant’s mental illness. 

Court Punishments for Individuals With Mental Illness

If the defense is successful in securing a ‘not guilty by reason of insanity’ verdict, the court will order the defendant to be committed to a mental health facility for a period of up to 120 days. During this time, examinations will be conducted to determine the need for ongoing hospitalization. If medical experts determine that the defendant no longer requires hospitalization, they may be released under specific terms established by the court. 


If a ‘guilty but mentally ill’ verdict is given, the court will consider the individual’s mental health problems and history during sentencing. It may also order that the defendant be held in a special facility at the Department of Corrections until they are deemed fit to be moved into a general prison.

In Summary

If you have questions about your own mental health, reach out to a clinical psychiatrist or a medical expert for guidance. If you are facing criminal charges and need legal representation, contact Strom Law’s highly qualified attorneys today. We are well-versed in what the four major criminal law defenses are and will work with you to develop a strategy for the best outcome possible, given the circumstances of your case!




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