One of the consequences of the public outcry over the 1929 St Valentine’s Day massacre was the establishment of a Scientific Crime Detection Laboratory at Northwestern University. The photogenic ‘Lie Detector Man’, Leonarde Keeler, was the laboratory’s poster boy, and his instrument the jewel in the crown of forensic science. The press often depicted Keeler gazing at a female suspect attached to his ‘sweat box’, a galvanometer electrode in her hand, a sphygmomanometer cuff on her arm and a rubber pneumograph (...) tube strapped across her breasts. Keeler’s fascination with the deceptive charms of the female body was one he shared with his fellow lie detector pioneers, all of whom met their wives – and in William Marston’s case, his mistress too – through their engagement with the instrument. Marston employed his own ‘Love Meter’, as the press dubbed it, to prove that ‘brunettes react far more violently to amatory stimuli than blondes’. In this article, I draw on the psychoanalytic concepts of fantasy and pleasure to argue that the female body played a pivotal role in establishing the lie detector’s reputation as an infallible and benign mechanical technology of truth. (shrink)