Thursday, September 3, 2009

Court decision upholds MR diagnosis in death penalty case: Davis v US (2009)

A recent US District Court decison (District of Maryland) was handed down April of this year (2009). Davis v US has been added to the Court Decisions section of this blog (see right-hand side of blog page).

In this case, the defendant was ruled to be MR and thus, was not eligible for the death penalty. Reading this decisions gives important insights re: how the courts weigh and judge conflicting expert testimony and evidence re: IQ scores and adaptive behavior. It is interesting to see how the court accepts or does not agree with different expert testimony and how it attends to the two primary professional definitions (AAMR/AAIDD APA) of MR.

Of interest re: IQ scores are discussions of the importance of full scale global IQ scores in the context of sub-composite discrepancies (Verbal vs Performanc IQ) and the relevance of the Flynn Effect. Also of interest is how the subjects history was used to establish MR during his developmental period (before age 18), the third prong of the accepted MR definitions (IQ deficit; adaptive behavior deficit; MR originating before age 18).

1 comment:

  1. The Davis opinion offers a very elegant analysis of the types of proof required in an Atkins determination. Notably, the court rejected the notion that only a "flat" IQ profile is characteristic of Intellectual Disabilities. In California, which does not have a "bright line" number for the determination of the intellectual deficits prong for MR, the Vidal case [] illustrates how extreme the discrepancies between verbal and performance abilities can be. Vidal was measured at one point as having a WAIS-R VIQ of 70, a PIQ of 96 and an FSIQ of 78. Other testing was even more extreme. It was argued and held at trial that Mr. Vidal was Mentally Retarded. The court of appeals was unwilling to overturn the trial courts opinion. Both of these cases look to the variability within an intellectual profile. The Floyd article cited by Dr. Walrath addresses this question effectively.


    Dale G. Watson, Ph.D.
    Clinical and Forensic Neuropsychologist
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