Well, some are here.

If you really need more numbers, then by all means go ahead and look them up yourself. They may or may not be available on the net. I've been unable to find them in a short, cursory look, and I don't feel like going down to the Franklin County Prison Library just to look them up. All I can freely relate is my personal experience in the matter.

I do know that the effectiveness of most interrogative techniques depends upon building an unsettling effect for the prisoner. The methods I described above do this. It should be recalled that the interrogative procedure is a generally disturbing one to most people who might be encountering it for the first time. It is the aim of the interrogator is to further enhance this effect, while at the same time creating a possibly, though not necessarily, traumatic experience for the prisoner, one which effectively destroys the true world that is familiar to the subject, as well as the subject's self image within that world.

A direct approach is normally used to interrogate a subject whose guilt/involvement in something (anything, really) is reasonably certain. In this approach, one assumes an air of confidence in a certain prisoner's sure guilt of something, stressing real/fabricated evidence/testimony indicative of the prisoner's guilt/association. The interrogator acts in an accusatory manner, displaying complete belief in the prisoner's guilt -- but the interrogator will not press for a confession of any sort, directing the flow of questioning so as to make it clear that all he really wishes to know is why the prisoner committed such a heinous offense, not if the prisoner committed the offense. From here will come an intimated admission of guilt, and the intelligence that follows may include such important items as names/locations of coconspirators, underlings, and supervisors; locations for weapons caches; and future plans of offensive organizations.

Anyway, reading through FM 34-52 (something I've not done in nearly 20 years), Appendix H describes the Direct Approach as being the most effective:

The direct approach is often called no approach at all, but it is the most effective of all the approaches. Statistics tell us that in World War II, it was 85 percent to 95 percent effective. In Vietnam, it was 90 percent to 95 percent effective.

Dan