Competency to stand trial is a legal term that indicates that the defendant in a trial must have the intellectual and emotional ability to distinguish right from wrong and be able to assist in their own defense. Under this heading, an individual is demonstrably mentally ill, of such low intelligence or of such an emotionally impoverished background that he is incapable of understanding that his actions were wrong. Proving that an individual is incompetent to stand trial is a controversial legal strategy that is usually quite difficult to prove.