I Missed That Class in Medical School

Actually I never went to medical school but perhaps someone who did can tell me when they learn to apply their dark arts in this fashion:

SEN. COBURN on Roberts: I've tried to use my medical skills of observation of body language to ascertain your uncomfortableness and ill at ease with questions and responses. I will tell you that I am very pleased both in my observational capabilities as a physician to know that your answers have been honest and forthright as I watch the rest of your body respond to the stress that you're under.
MR. RUSSERT: Do you believe as a physician you can tell whether a candidate for the Supreme Court is telling the truth?

SEN. COBURN: Mm-hm, I certainly have.

MR. RUSSERT: Has any--have you ever detected someone lying?

SEN. COBURN: Uh-huh, lots of times.