Functional Magnetic Resonance Imaging allows real time monitoring of brain activity by measuring the level of blood flow to areas of the brain. Given this advance in technology allows us to peer into the brain when thoughts are made, could it also be used to detect deception? There are many who argue fMRI should be used in criminal investigations to aid lie detection. However, there are good reasons to be skeptical. Interpretation of fMRI images is still a challenge, and the images gained for ‘lying’ via fMRI have shown to be culturally varied. For these reasons, fMRI lie detection has failed admissibility as expert evidence via the Daubert standard in US courts, and also why it is unlikely to be admissible in Australian courts.