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The Jodi Arias Defense Expert: More Myths About Psychology and Mental Health Assessment

March 23, 2013

Thursday, Richard Samuels, the defense psychologist expert witness in the Jodi Arias case answered questions from the jury and was then once again questioned by the defense and then the prosecution began a re-cross examination of him. A common theme throughout his testimony is how many years of experience he has had and the assertion that this makes him more credible and accurate at what he does when he assesses and diagnoses people. As I have written previously, the scientific evidence shows that this is not necessarily the case.

Samuels and the defense counsel trying to play the experience card, I suspect is a way subtle way for them to take a swipe at the prosecution’s rebuttal expert. Although I haven’t seen her full CV, she is obviously much younger and a more recent PhD (2009). Does this mean that her opinion is inferior to Samuels? Research evidence says not necessarily. She might actually have an advantage over Samuels, being more recently in school and being more up on the latest research. Some of the statements made by Samuels displayed an astonishing ignorance of developments over the last decade or so. For example, he testified that sodium pentathol and hypnosis were good ways to recover repressed memories when these methods have been discredited as unreliable and even dangerous because they may produce false memories and do great harm. Even though he made it clear he didn’t think Jodi Arias had repressed memories, he still presented these myths to the jury about what he thought was a good idea for people who did have them. He thought Jodi Arias had dissociative amnesia, due to the hippocampus shutting down completely during the part of the murder she says she cannot remember. That too, is a highly questionable notion, as the literature shows that this is very rare and when amnesia does occur during a murder, it is usually temporary. More typically trauma is very well remembered and people with PTSD have the opposite problem — they wish they could forget the trauma but cannot stop thinking about it.

Samuels would do well to review the literature on psychological assessment and whether psychologists learn well from experience and improve. There is quite a large body of literature showing that this is not the case and also how unreliable clinical judgment is. He was correct to call it “speculation” and Juan Martinez was very correct to pin him down on what he said. Some of this literature is reviewed in Howard Garb & Patricia Boyle’s chapter in Scott Lilienfeld’s edited volume, Science and Pseudoscience in Clinical Psychology on “Understanding Why Some Clinicians Use Pseudoscientific Methods” (2nd Edition to be published soon). Garb & Boyle discuss experienced vs. less experienced clinicians. They write:

For the task of interpreting personality assessment test results, alleged experts have not been more accurate than other clinicians, and experienced clinicians have not been more accurate than less experienced clinicians.

They cite a large body of literature accumulated over 30 year period that supports this. One of the examples they provide is about one of the tests used by the Jodi Arias defense, the MMPI. Two groups of psychologists were presented with MMPI protocols. One group consisted of PhD psychologists who had routinely used the MMPI in practice for 5 years, the other group were psychologists who had used the MMPI for over 5 years and demonstrated a broad knowledge of the research literature. Both groups were asked to interpret the MMPI. The findings showed that the psychologists with more experience were no more accurate in their interpretations than the group with less experience. The two were completely unrelated.

We can only hope that the prosecutions’ expert Janeen Demarte is aware of this literature so she can soundly refute any attempts by the defense to make less of her by claiming that because she has less years of experience than Samuels, she is not as credible — this is absolutely false.

Once again, we are seeing myth after myth presented on national television for all to see, although for the purposes of this case, from the juror’s questions that were asked last Thursday, it doesn’t look like the defense has been very successful in persuading the jury of his credibility.

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One Comment
  1. I totally agree. My hope is that the prosecution expert will bring back some credibility to our profession that has taken a big hit with Samuels.

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