Through a Scanner Darkly: Functional Neuroimaging as Evidence of a Criminal Defendant's Past Mental States

91 Pages Posted: 15 May 2009 Last revised: 3 Feb 2013

See all articles by Teneille R. Brown

Teneille R. Brown

University of Utah - S.J. Quinney College of Law

Emily R. Murphy

UC Hastings Law

Date Written: May 21, 2009


As with phrenology and the polygraph, we are again confronted with a device that the media claims to be capable of reading our minds. This new device is functional magnetic resonance imaging ("fMRI"), and it is currently being introduced to negate a criminal defendant's mens rea, such as the specific intent to kill. In this paper we will demonstrate that functional brain images should not currently be admitted into courts for this purpose. We will do so by walking through each step of the imaging methodology in plain terms, making it clear why the brain images are minimally probative when introduced to prove a defendant’s mens rea, and almost certainly substantially more prejudicial than probative on balance. Our commitment to staying close to the science is what separates our article from others, as the previous articles do not spend enough time engaging with the methodology, and in so doing they espouse a far too rosy picture of its probative value. While further research needs to be conducted on mock jurors, preliminary findings suggest that the mere presentation of brain images can make a bad argument appear more sensible. We address other forms of prejudice as well, such as fMRI's potential to mislead jurors and waste the court's resources. As the methodology may one day improve such that the probative value is no longer eclipsed by the extreme potential for prejudice, we offer at the end a non-exhaustive checklist that judges or counsel can use to authenticate the functional brain images and assess the weight these images are to be accorded by fact-finders.

Keywords: neuroscience, fMRI, mens rea, 403, prejudicial evidence, mind reading, neuroimaging, brain images

Suggested Citation

Brown, Teneille R. and Murphy, Emily R., Through a Scanner Darkly: Functional Neuroimaging as Evidence of a Criminal Defendant's Past Mental States (May 21, 2009). Stanford Law Review, Vol. 62, 2010, Gruter Institute Squaw Valley Conference 2009: Law, Behavior & the Brain, Available at SSRN:

Teneille R. Brown (Contact Author)

University of Utah - S.J. Quinney College of Law ( email )

383 S. University Street
Salt Lake City, UT 84112-0730
United States

Emily R. Murphy

UC Hastings Law ( email )

200 McAllister Street
San Francisco, CA 94102
United States

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