Asserting Mental Disease or Defect in a Criminal Prosecution (On-Demand)

General Credits:
Original Date Of Course:



Course Description

This course will examine the affirmative defense of mental disease or defect in a criminal prosecution.  We will explore the legal definition of mental disease, and how that differs from a clinical definition.  We will discuss what a defendant has to establish to assert the defense, the mechanics of the claim, address the difference between the mental disease defense and a claim that a defendant is not competent to stand trial.

We will discuss the difficulties with the defense, why it is so infrequently used despite the high prevalence of mental disease among those arrested for crimes, and why the success rate is so low when it is asserted.  We will examine a few well known examples of criminal cases where mental illness played a key role, and explain how those cases were resolved and why.


  1. Introduction
  2. What is an affirmative defense
  3. Penal Law § 40.15 – the affirmative defense of mental disease or defect
  4. The defendant’s role in asserting the defense
  5. The legal mechanics of the mental disease defense, the requirements a defense attorney has to meet
  6. The role of the expert evaluation and whether it is necessary
  7. The effect of a defendant’s refusal to participate in an evaluation
  8. Legal v. clinical mental disease
  9. Competency to stand trial v. mental disease
  10. Mental illness and pro se representation
  11. A few examples of mental diseases commonly claimed when asserting the defense
  12. What happens when the judge/jury agrees and credits the mental disease defense
  13. Some high profile examples of trials focused on mental disease
  14. The future of the defense and improvements that can be made to the system


Paul Townsend, Esq.

Credit Details

Course Type

Course Instructor

Paul Townsend, Esq

Original Date Of Course

General Credits