Ah, the fabled "truth serum." You don't have to watch many Hollywood movies to find out that you can get the bad guy to reveal his lie by injecting him with sodium thiopental. It all seems a bit far-fetched, but some police forces still use the drug, which was first developed in the 1930s as an anaesthetic. The drug has similar effects as alcohol, reducing some brain functions and generally reducing inhibition — which ultimately makes people more chatty, and hopefully, more likely to tell the truth. The BBC's Michael Mosley has decided to put it to the test, trying to keep to his lie that he's a world famous cardiac surgeon under interrogation. As you can see in the video over at The BBC, his lie certainly becomes less-than-convincing, but what happens when the doctors upped the dosage is particularly interesting.