"In this case, Dr. Martell was asked to evaluate Defendant's vulnerability to change his answers, his suggestibility, and malleability as applied to a police interrogation. Dr. Martell testified that he evaluated Defendant for about three hours focusing on the Gudjonsson Suggestibility Scale ("GSS"), memory testing, tests for malingering, and a neuropsychological interview. After evaluating Defendant, Dr. Martell opined that Defendant had difficulties in school, a verbal comprehension deficiency, and likely has a learning disability in reading and math.
Dr. Martell described the GSS suggestibility scale as a test of the degree of vulnerability a person has to suggestions that may contaminate or influence that person's ability to recall an event. According to his testimony, a person's degree of suggestibility is permanent, but being high on heroin or other factors could temporarily make someone more suggestible. The test is administered by telling the subject a story, asking the subject to recall the story from memory, asking the subject to recall it again after thirty minutes, and then asking the subject a series of suggestive questions that may or may not be answerable from the story. After the questions, the test administrator determines a score based on how many mistakes the subject made and then asks the subject to answer the questions again and to try to be more accurate. The administrator uses this process to develop a yield score, i.e. a measure of how much the subject yields to suggestion. For example, after initially being asked "Did the assailant in the story use knives or guns?" and answering "guns," the subject is again asked the same question. If the subject responds by saying "knives" the second time, then the yield score is greater, showing an increased propensity to yield to suggestion. The GSS provides, among other things, a "shift score" which measures the subject's susceptibility to change (shift) his answers after being admonished by the test administrator."