In some cases when someone suffers a severe head injury or has an extreme mental condition that impairs his or her ability to form intent, they may assert a diminished capacity defense. With respect to a diminished capacity defense, according to State v. Ellis (Number 65761-1, October 1998) the Supreme Court determined that:

• To maintain a diminished capacity defense, a defendant must produce expert testimony demonstrating that a mental condition, not amounting to insanity, impaired the defendant’s ability to form the requisite intent to commit the crime charged.
• Evidence of the mental condition must be substantial and logically and reasonably connect the defendant’s alleged mental condition with the inability to possess the required level of culpability to commit the crime charged

A person acts with intent or internationality when he acts with the objective or purpose to accomplish a result, which constitutes a crime. Inability to form a specific intent must occur at a time relevant to the offense.