As with phrenology and the polygraph, society is again confronted with a device that the media claims is capable of reading our minds. Functional magnetic resonance imaging ("fMRI"), along with other types of functional brain imaging technologies, is currently being introduced at various stages of a criminal trial as evidence of a defendant's past mental state. This Article demonstrates that functional brain images should not currently be admitted as evidence into courts for this purpose. Using the analytical framework provided by Federal Rule of Evidence 403 as a threshold to a Daubert/Frye analysis, we demonstrate that, when fMRI methodology is properly understood brain images are only minimally probative of a defendant's past mental states and are almost certainly more unfairly prejudicial than probative on balance. Careful and detailed explanation of the underlying science separates this Article from others, which have tended to paint fMRI with a gloss of credibility and certainty for all courtroom-relevant applications. Instead we argue that this technology may present a particularly strong form of unfair prejudice in addition to its potential to mislead jurors and waste the court's resources. Finally, since fMRI methodology may one day improve such that its probative value is no longer eclipsed by its extreme potential for unfair prejudice, we offer a nonexhaustive checklist that judges and counsel can use to authenticate functional brain images and assess the weight these images are to be accorded by fact finders.
INTRODUCTION I. FUNCTIONAL NEUROIMAGING FOR MENS REA CLAIMS A. What Is Functional Neuroimaging? B. Mens Rea Claims C. Present and Anticipated Future Use of Functional Brain Imaging in Courts D. The Impact of Neuroscience on the Law: Grounding in Evidence II. SCIENTIFIC BACKGROUND: IMAGING BRAIN ACTIVITY AND MENTAL STATES A. The Science of Functional Neuroimaging 1. Overview of older methods 2. Principles of fMRI 3. Knowns and unknowns about the BOLD response 4. The semantics of "activation" B. The "Function" of Functional Imaging: Task Dependency and Behavior C. Variables in Data Collection, Processing, and Analysis 1. Hardware and software: the scanner 2. Processing the raw data 3. Individual differences and reliance on the group data a. Something with which to compare." defining "normal" b. Individual differences are important but are often ignored 4. Variance: the statistical threshold can be manipulated to affect the results 5. Variance: the statistical analysis employed can affect the results III. LEGAL ANALYSIS A. Admissibility Is Specific to the Evidentiary Purpose B. Classifying Functional Brain Images C. Relevance 1. Logical inference and relationships between brain data and mental states D. Authentication 1. The pictorial and silent witness theory of admissibility may accommodate the authentication of fMRI images 2. Images must accurately capture the individual's brain under the same conditions that existed at the time of the crime 3. The procedure for creating the image should be described in detail to remove any possibility of tampering, error, or distortion 4. Underlying statistical computer programs must demonstrate reliance on irrefutable scientific principles 5. Authentication should be specific to fMRI and distinct from other image types E. Why Daubert, Frye, and FRE 702 Should be Secondary Considerations After Rule 403 F. Probative Value 1. fMRI has limited probative value unless the question of proper base rates is resolved 2. fMRI has limited probative value as it relies on averaged group data and ignores individual differences 3. fMRI will have limited probative value for determining mens rea until we know more about the BOLD response 4. fMRI will have limited probative value for the purpose of determining mens rea until we have standardized methods for processing the data and creating the activation map 5. fMRI will have limited probative value for the purpose of determining mens rea so long as institutional review boards exist and research ethics are followed 6. fMRI has limited probative value for evaluating past mental states as it measures present reactions to present stimuli 7. Multiple steps in the chain of inference severely limit the probative value of fMRI G. Unfairly Prejudicial Effect and the Role of FRE 403 . 1. fMRI images may be overvalued due to their glossy portrayal of "hard science" 2. fMRI gives the unfairly prejudicial illusion that you are directly observing the brain's activity 3. fMRI is unfairly prejudicial as the probative content will be presumed based on what the image can prove and what it appears to prove 4. fMRI images may be unfairly prejudicial based on neuro-essentialism 5. fMRI has low probative value because alternative, better means of proof exist a. The first alternative to fMRI evidence is the defendant's behavior at the time of the crime b. Another alternative is behavioral psychology 6. fMRI is unfairly prejudicial as it encourages the fundamental psycholegal error 7. fMRI evidence is unfairly prejudicial as it impairs factfinders' ability to assess evidence H. Cross-Examination Is Not the Cure CONCLUSION A. FRE 403 Provides Adequate Grounds for Exclusion Based on the Potential for Unfair Prejudice and Nearly Bankrupt Probative Value B. Closing Thoughts on the Critical Legal View of the Allure of fMRI APPENDIX: CHECKLIST FOR JUDGES CONFRONTED WITH FUNCTIONAL NEUROIMAGING EVIDENCE INTRODUCTION
Intent is basically a subjective element, that is, the operation of a person's mind. However, since we cannot x-ray a person's mind to determine what he is thinking, you may infer a person's intent by his acts or words or both. (1) The model jury instruction above tantalizes those who hope to use technology to improve upon current methods of determining what is in someone's mind. We now know that x-raying a person's brain does not provide direct access to her mind, but that was not always the case. (2) As with phrenology (3) and the polygraph (4) before, courts are again confronted with a technology that the media claims is capable of mind reading: functional neuroimaging. A recent criminal case in California provides an example of the attempted use of functional neuroimaging to address what was--or was not--going on in a defendant's mind at the time of the crime.
In Monterey County, defendant Francisco Savinon was charged with attempted murder. (5) After the dissolution of his long-term relationship and the loss of his job, Savinon became increasingly despondent and decided to commit suicide. He testified that while sitting in his car inhaling carbon monoxide fumes from the exhaust pipe, he "remembered" that a "recurring theme" in conversations with his ex-girlfriend (Jane Doe) was that "if they could be alone, free of kids and former spouses and the daily stresses of life--they would be happy." (6) Savinon claimed that in his altered state of consciousness, due to alcohol intoxication and carbon monoxide exposure, he decided "this [recurring theme] meant she wanted to die with him and they would both be happy if they went to heaven together." (7)
Savinon got into a second car, drove to Jane Doe's condo, and waited for her to emerge. When Jane Doe left her building, Savinon attacked her and took her at knifepoint in her own car to his apartment. When she gained awareness of her surroundings and struggled against him, he stabbed her at least twice before forcing her into his car. He duct-taped her to the passenger seat and attempted to poison them both with the exhaust fumes. Jane Doe managed to convince him not to kill them both. Savinon released her on the condition that she promised not to tell anyone who attacked her. Savinon then bandaged her wounds and took her back to her apartment, where he brought her a cordless phone so she could call 911. (8)
Savinon entered pleas of not guilty and not guilty by reason of insanity, based on a claim that due to his psychiatric diagnosis of major depressive disorder and his acute carbon monoxide exposure, he was cognitively impaired and thus could not have formed the required mens rea for attempted murder. (9) The defendant's claims were to be supported by family testimony, psychiatric clinical testimony, and by images from a functional neuroimaging device known as single proton emission computerized tomography (SPECT) machine. (10) Dr. William Klindt of San Jose Brain Clinic obtained the SPECT images about five months after the incident. (11)
Functional neuroimaging devices like SPECT are not generally accepted in the medical or scientific community for the purpose of validating depression. (12) Even so, Dr. Klindt was prepared to assert that SPECT's appropriate neurological uses transferred validity to other as-yet unproven forensic psychiatric uses. (13) It is improper for advocates to blur together the multiple uses of a technology such as functional neuroimaging. (14)
In addition to highlighting the way functional neuroimaging may be coopted by parties to a case, the Savinon case also illustrates the important and practical impact of resources in the adversarial system. Despite the prosecution's having a written affidavit by a respected SPECT expert (15) refuting the validity of SPECT for forensic psychiatric purposes, the district attorney's office did not have the funds to pay for this expert to travel to the Bay Area for both the pretrial evidentiary hearing and, if admitted, the actual trial itself. Understandably, the prosecutor facing the pretrial hearing was worried that the paper testimony from her expert would not be as persuasive as the defense expert's oral testimony and accompanying colorful brain images. (16)
At the time of this writing, data are being gathered to assess the frequency of neuroimaging-based evidence offered or accepted in court. (17) Anecdotal reports such as the Savinon case lead us to hypothesize that functional brain images are showing up with...