Brain imaging and courtroom evidence: on the admissibility and persuasiveness of fMRI

Functional magnetic resonance imaging (fMRI) is currently the most advanced technique for measuring and depicting brain function. Functional MRI studies abound in neuroscience, psychiatry and psychology. Inevitably, fMRI-based evidence will be offered in court as proof of matters involving parties' mental states and capabilities. This paper analyses the likely admissibility of fMRI testimony and images. Cases involving other types of functional neuroimaging (PET and SPECT), which may shed light on judges' receptivity to fMRI evidence, are briefly surveyed. The conceptual and methodological underpinnings of fMRI are then explored, prompting basic questions about the evidentiary reliability and relevance of fMRI results. The first reported case involving fMRI evidence, which raises several of these questions, is described. Finally, the admissibility and probative value of the fMRI images themselves are discussed. Assuming that the expert testimony that the images are offered to illustrate is admissible, it is argued that the law can obtain the benefits of fMRI science while minimising the judgmental risks by allowing triers of fact to see the images and encouraging experts and lawyers to educate the triers to interpret the images properly.