Malingering Versus Genuine Amnesia in a Murder Defense
Ms. T, 29, is charged with the stabbing death of her partner. She claims complete amnesia for the 40 minutes surrounding the killing. She has no documented head injury, no seizure history, and a negative toxicology screen. On the Test of Memory Malingering she scores 48, 49, and 49 across three trials; on a forced-choice symptom validity test she performs below chance (p < .05). During the interview she spontaneously describes the victim's 'surprised face' and then, minutes later, states she remembers 'nothing at all' about the incident. She has a prior conviction for fraud and is facing a life sentence.
1. Evaluate the validity data. What do below-chance forced-choice performance and the TOMM pattern indicate, and how should the evaluator weigh them against the possibility of genuine dissociative amnesia?
Read the worked answer
Below-chance performance on a forced-choice SVT is the strongest available signal of intentional feigning: a genuine amnesic or impaired examinee performs at or above chance because guessing yields ~50%. Scoring significantly below chance implies the examinee knows the correct answer and avoids it. The TOMM pattern (48/49/49) is within normal limits and does not support feigning on that instrument - but passing one SVT does not rule out feigning on other domains, and SVTs measure effort, not amnesia specifically.
The evaluator should not rest on a single instrument. The decisive evidence is the internal inconsistency: spontaneous, sensory-rich recall of the victim's face followed by denial of any memory. Genuine dissociative amnesia for a violent act is possible but is typically patchy and not selectively reversed within minutes under interview pressure.
The conclusion should be that the amnesia claim is not credible, with feigning documented across multiple indicators (below-chance SVT, inconsistent report, external incentive). The evaluator must state the limits: this is a psycholegal opinion about the credibility of a symptom report, not a finding of guilt.
2. Defense counsel asks the evaluator to state that Ms. T 'could not have formed the intent to kill because she was in a dissociative state.' How should the evaluator respond, and what is the boundary between the evaluator's role and the jury's?
Read the worked answer
The evaluator should decline to offer that opinion as framed. Two problems: (1) the empirical basis is absent - the amnesia claim is not credible, so there is no reliable foundation for a dissociative-state opinion; and (2) the requested statement is an ultimate legal conclusion about intent, which is the factfinder's province, not the evaluator's.
The evaluator can properly testify to clinical and behavioral findings - the validity data, the inconsistency, the absence of neurological or toxicological corroboration - and may explain, in general terms, what a genuine dissociative state would look like and why the observed presentation does not fit it. That is within expertise.
The response should be documented and communicated to retaining counsel in writing: the evaluator will describe findings and their limits, will not opine on whether the defendant formed intent, and will not adopt counsel's characterization. If pressed, the evaluator should note that an opinion on the legal element of intent would exceed the scope of the retained role and risk usurping the jury.