Lie detector
A lie detector could detect if the subject was being untruthful.
Jack Harkness used what he described as "the best lie detector on the planet" on Ianto Jones to determine if he was telling the truth about murdering three women. The test read what he was saying as truth. In actuality, these were false memories implanted by Adam Smith. (TV: Adam [+]Loading...["Adam (TV story)"])
Noah used a lie detector on River Song shortly prior to the Nerva Beacon's departure from Earth's space. (AUDIO: Last Words [+]Loading...["Last Words (audio story)"])
Anya Kingdom used a lie detector on Ellasi Craig to determine whether or not she was a Dalek agent. The detector confirmed that she was not. (AUDIO: The Dalek Protocol [+]Loading...["The Dalek Protocol (audio story)"])
The Judas Gift was a Draconian lie detector. (AUDIO: The Judas Gift [+]Loading...["The Judas Gift (audio story)"])
