- Published: November 30, 1999
A recurring theme in the field of neurolaw is whether or not functional neuroimaging techniques are appropriate for use in different capacities in a legal forum. In a recent paper this year in the Journal of the American Academy of Psychiatry and the Law, Dr. Robert Granacher specifically discusses the role of single photon emission computed tomography (SPECT) and positron emission tomography (PET) in the diagnosis of mild traumatic brain injury (MTBI), and the scientific validity of these functional neuroimaging techniques within the context of civil litigation. The reason the diagnosis of MTBI is of concern to lawyers and neuroscientists is because the definition of MTBI is not at a consensus amongst neuroscientists and neurologists due to the subjectivity involved in its diagnosis. This undefined characteristic of MTBI provides an opportunity for parties to present subjective data in litigation, in the form of symptoms resulting from MTBI. This has led to a recent trend in the medical literature, where significant evidence has been found suggesting that 39% of people litigating post-MTBI have a high likelihood of exaggerating and prolonging symptoms in order to maximize compensation. This is just one example of why there is a need for litigation issues and the neuropsychiatric validity of MTBI to be examined within a legal context.
In a 1993 case, Daubert v. Merrell Dow Pharmaceuticals, Inc., two families with sons with birth defects sued Merrell Dow Pharmaceuticals, Inc., claiming that Bendectin, a drug prescribed to treat nausea and vomiting in morning sickness patients, had caused the birth defects in their children. In this case, Merrell Dow brought forth evidence showing no published scientific evidence demonstrating a link between Bendectin and birth defects. The families also brought forth their own evidence claiming there was a link; however, it was based entirely on in vivo and in vitro animal studies, pharmacological studies, and their own analysis of existing studies; none of which made a convincing argument because none of which had gained acceptance in the scientific community. The result of this case was the Daubert criteria, a list of 3 conditions that expert testimony must satisfy in order to be considered legally relevant – 1) the expert testimony must be grounded in scientific knowledge, 2) there must be “valid scientific connection to the pertinent inquiry as a prerequisite to admissibility”, and 3) there must be general acceptance of the theory and technique within the scientific community. It is because of this third condition that Granacher argues that SPECT and PET neuroimaging should not be admitted in court as a stand-alone diagnostic test for MTBI. SPECT and PET are able to detect cerebral blood flow and metabolic changes following MTBI, but cannot indicate a causal relationship between these changes in neurophysiologic function and lesions because of the known error rates that make such correlations scientifically invalid. Furthermore, there is a long list of false negatives – results due to patient medications, substance abuse, pre-existing psychiatric conditions, prior head trauma, etc. – associated with MTBI diagnosis from functional neuroimaging. Thus, SPECT and PET lack the diagnostic precision necessary to clinically correlate functional neuroimaging to MTBI.
Personally, I agree completely with the message Dr. Granacher is trying to get across in his recent paper. I don’t believe that we should stretch the influence of relatively new neuroimaging techniques if their results are inconclusive and are not supported by the relevant scientific community. Dr. Granacher is correct in suggesting that it is not only unethical, but also improper and impractical to use these neuroimaging techniques as sufficient stand-alone evidence in cases regarding MTBI. However, I feel it important to note that SPECT and PET can serve as legitimate supporting evidence in a case when paired with structural neuroimaging (CT or MRI) to show a strong clinical correlation of MTBI. While it is important to take a strong stance against the inappropriate use of unsubstantiated neuroscientific evidence in the courtroom, I find it equally important that we not forget the worth of developing technology. As long as we understand the technology’s current limitations and use it as evidence in the legal forum only when appropriate, functional neuroimaging can prove to be a very valuable resource in the diagnosis, and subsequently, the possible legal implications, of MTBI.