A downward departure may be warranted if (1) the defendant committed the offense while suffering from a significantly reduced mental capacity; and (2) the significantly reduced mental capacity contributed substantially to the commission of the offense.  Similarly, if a departure is warranted under this policy statement, the extent of the departure should reflect the extent to which the reduced mental capacity contributed to the commission of the offense.

However, the court may not depart below the applicable guideline range if (1) the significantly reduced mental capacity was caused by the voluntary use of drugs or other intoxicants; (2) the facts and circumstances of the defendant's offense indicate a need to protect the public because the offense involved actual violence or a serious threat of violence; (3) the defendant's criminal history indicates a need to incarcerate the defendant to protect the public; or (4) the defendant has been convicted of an offense under chapter 71, 109A, 110, or 117, of title 18, United States Code.

"Significantly reduced mental capacity" means the defendant, although convicted, has a significantly impaired ability to (A) understand the wrongfulness of the behavior comprising the offense or to exercise the power of reason; or (B) control behavior that the defendant knows is wrongful.