And to what extent does waterboarding leave permant physical injuries or scars? Waterboarding pushed the limits of what can be determined to be short of torture, but does not cross that limit. At least so our courts have ruled.
Torture is not definitely tied to permanent physical disability or scarification. Please see the legal definition below as explained in the US Code. But anyways, to answer your question. Waterboarding can cause lung damage, dry drowning, brain damage due to asphyxiation, severe psychological damage or death. Secondary damage of severe bruising and broken bones nearly always occurs due to involuntary struggling or spasms unless medical restraints are used to immobilize the subject.
Actually, James Parker might disagree on court ruling waterboarding as being legal. He was the Texas Sheriff for San Jacinto County sentenced in 1983 to ten years in prison for using that method on suspects. (744 F.2d 1124; 1984 U.S. App. LEXIS 17759) Or Major Littleton Waller, USMC. During the Spanish-American War, he was court martialed for, among other things, using waterboarding to interrogate Filipino guerrillas. In White vs. State (129 Miss. 182; 91 So. 903 (1922)), Gerrard White's conviction was overturned as it was coerced by means of waterboarding. Same again for John Fisher (Fisher v. State, 145 Miss. 116; 110 So. 361 (1926)). A soldier from 1st Cav was court martialed during Vietnam for waterboarding a detainee, convicted Feb. 28, 1968.
As for the law. Torture is defined under Title 18, Part I, Chapter 113C, § 2340. (
Link). For military personnel, they are subject to the UCMJ (Article 93). There is also the War Crimes Act (18 U.S.C. § 2441), which specifically covers Torture under § 2441 (d)(1)(A) (
Link).
The previous administration based their legal interpretation of torture on the findings of John Yoo, formerly of the Office of Legal Counsel. Said findings were immediately retracted by a Mr. Jack Goldsmith, his replacement at OLC, for being legally flawed. I have a copy of Mr. Yoo's book, War by Other Means, which was written in a tone that the author was obviously a lawyer. I don't recommend it, literary wise. Very poorly written, ironically.