How does truth serum work on the body?

According to information obtained by public disclosure, truth drugs are highly unreliable, with subjects apparently freely mixing fact and fantasy. Much of the claimed effect relies on the belief of the subject that they cannot tell a lie while under the influence of the drug. It has also been said that the use of a truth serum such as sodium amobarbital does not increase truth-telling, but merely increases talking; therefore, truth is more likely to be revealed, but so are lies.

http://en.wikipedia.org/wiki/Truth_drug

I can’t resist answering something!

Truth Serum is a kind of bogus name for a number of different sedatives. The Germans during WWII used Scopolamine, one of the Belladonna alkaloids, as a truth agent. Sodium pentathol has also been used. The idea is to make you sleepy and loopy and more pliable to suggestion. It doesn’t compel you to tell the truth, as suggested in the Schwarzenegger film True Lies. Anyone trained as an operative would be able to resist its effects, which is why interrogators resort to grislier methods of extracting information. However, it’s also been shown that torture is not a particularly reliable method, either.

Uh-oh. They’re banging on my door, there’s a big black Suburban parked outside. Gitmo, here I come!

my understanding is that lying is a much harder process cognitively than spouting facts on prompting…. the drugs disable higher centers of the brain, so the subject is less able to predict what his inquisitors want to hear, and then formulate a tailored lie for the occasion.

This is a comment, not an answer. Seeing that someone mentioned that the suggestion of effectiveness could make the subject more likely to tell the truth, did anybody read the article about a small town police department (can’t remember where) who created their own “lie detector” by placing a colander upside down on a suspect’s head and attaching it (seemingly) to a copier? Every time that the suspect gave information that they didn’t want to hear, they’d press the “copy” button and a piece of paper with the text “HE’S LYING” would shoot out. The suspect confessed to his crime. It was in one of the News of the Weird sections on MSNBC, I believe.