Insanity

There's quite a lot to know about the insanity defense should it show up on the MBE. There are different tests to determine whether at the time of the crime the defendant's mental illness should entitle the defendant to an acquittal. But in addition to that, there are also quite a few procedural details that could show up in the questions. First, the tests:

The M'Nagten Rule: Under this rule, a defendant is entitled to acquittal if a disease of the mind caused a defect of reason such that the defendant lacked the ability at the time of his actions to either know the wrongfulness of his actions or understand the nature and quality of his actions. It's important to understand that this rule applies if either the defendant didn't know that his acts were wrong or didn't understand the nature/quality of those acts.

Irresistible Impulse Test: Under this test, a defendant is entitled to acquittal only if because of a mental illness, defendant was unable to control his actions or conform his conduct to the law. Inability to control is the key here.

Durham Test (Sometimes called the New Hampshire Test): Under this test, a defendant is entitled to acquittal if the crime was a product of the defendant's mental illness. This one is quite broad. It's called the New Hampshire test because it's followed only in New Hampshire. 

The Model Penal Code Test: Under this test, a defendant is entitled to acquittal if the defendant had a mental disease or defect, and, as a result, lacked the substantial capacity to either appreciate the criminality of his conduct or conform his conduct to the requirements of the law. 

Although it's essential to understand the above tests, questions are also sure to show up that deal with more procedural aspects of a claim of insanity. One area is burden of proof. All defendants are presumed sane; the defendant must raise the insanity defense. Usually once that issue is raised, the defendant must then prove insanity, and the burden to prove insanity is often by a preponderance of the evidence. Certainly worth noting, though, that the Model Penal Code instead requires that the prosecution prove that the defendant was sane, and the burden there will be beyond a reasonable doubt. Federal courts require the defendant to prove insanity by clear and convincing evidence. The defendant need not raise the insanity defense when a plea is taken; rather, a simple "not guilty" is sufficient, and that will not preclude later raising the defense. 

By not raising the insanity defense, the defendant may refuse a court-ordered psychiatric examination. If the insanity defense is raised, then refusal is not permissible. If the defendant does raise the defense and if the defendant is later acquitted by reason of insanity, he may be committed to a mental institution until cured. Confinement may even exceed the maximum period of incarceration for the charged offense. 

Lastly, it's worth noting a similar though different concept from the insanity defense called competency to stand trial. Under the Due Process Clause of the U.S. Constitution, a defendant may not be tried, convicted, or sentenced if, as a result of a mental disease or defect, defendant is unable to understand the nature of the proceedings brought against him or assist his lawyer in the preparation of a defense. Likewise, a defendant may not be executed if he is incapable of understanding the nature and purpose of the punishment,