U.S. Definition of Torture: 18 U.S. Code sec. 2340 (effective 1994)

 (1) “torture” means an act committed by a person acting under the color of law specifically intended to inflict severe physical or mental pain or suffering (other than pain or suffering incidental to lawful sanctions) upon another person within his custody or physical control;

(2) “severe mental pain or suffering” means the prolonged mental harm caused by or resulting from—

                (A) the intentional infliction or threatened infliction of severe physical pain or suffering;
                (B) the administration or application, or threatened administration or application, of mind-altering substances or other procedures calculated to disrupt profoundly the senses or the personality;
                (C) the threat of imminent death; or
                (D) the threat that another person will imminently be subjected to death, severe physical pain or suffering, or the administration or application of mind-altering substances or other procedures calculated to disrupt profoundly the senses or personality; and

“Whoever outside of the United States commits or attempts to commit torture shall be fined under this title or imprisoned not more than 20 years, or both, and if death results to any person from conduct prohibited by this subsection, shall be punished by death or imprisoned for any tem of years or for life.”

U.S. War Crimes Act (1996, 18 U.S.C. sec. 2441) imposes criminal penalties for “grave breaches” of the Geneva Conventions; the War Crimes Act affirms that refers “biological experiments” are illegal if they  “are not justified by the medical, dental, or hospital treatment of the prisoner concerned and carried out in his interest.”