Faking an insanity plea
How hard can it be?
Under Canada’s Criminal Code an individual cannot be held accountable for a crime if their mental state at the time made them “incapable of appreciating” the nature of the act and knowing that it was wrong.
Insanity pleas are rare — according to one study, less than 1% of defendants ever claim it and of that, only a quarter gain acquittals. But when an insanity plea can avert a death sentence, as is the case in some states in the US, the urge to appear mentally ill must be strong. So how do psychologists differentiate between those who are mentally ill and those who are simply faking it?
The M-FAST (Miller Forensic Assessment of Symptoms test) is a 10-minute test with 25 questions on symptoms both real and fake. Unless the test taker is actually mentally ill or a trained forensic psychologist, it would be impossible to pick the right combination of symptoms.
Another reliable test is the SIRS (Structured Interview of Reported Symptoms), which is a 172 item questionnaire that detects response styles associated with feigning illness. The test addresses specific symptoms and the reported severity, then addresses them again — to measure consistency.
Common signs of malingering (or “faking it”) are reports of exaggerated symptoms and the ignorance of more nuanced signs of mental illness, like the blunting of emotions. Some suspects, for instance, will claim to hear voices in their head, whose commands they are helpless to resist. This is in line with an exaggerated depiction of schizophrenia popularized in the movies. In reality, auditory hallucinations originate outside the head, not in; rarely are they commanding and schizophrenics are not totally helpless — they often find strategies to ignore these voices.
The MMPI (Minnesota Multiphasic Personality Inventory) is a measure of adult personality and psychopathology that has been used to detect faking. The validity scales in the MMPI-2 contain three types of validity measurements: (1) those designed to test for inconsistent or non-answered responses; (2) those designed to detect exaggerated prevalence and severity of symptoms and (3) those designed to test under-reporting of psychological symptoms (“faking good”).
In addition to psychometry, there are other ways to detect malingering. Mental illness does not develop overnight, so a history of hospitalizations is important to consider. Clues from the crime scene itself could also point towards a clear thinking, rather than a mentally ill individual. Interviews are also invaluable — the longer the suspect is allowed to talk, the more likely they are to lose track of their fabricated symptoms.
Insanity pleas may carry high stakes, but luckily, faking it is not as easy as it seems!