Measuring Mental Disability and Death Penalty Cases

This past Monday the Supreme Court agreed to hear a Florida
death penalty
case that deals with how states determine whether a death row
inmate is mentally disabled. In 2002, the Supreme Court ruled that it was unconstitutional
for states to execute someone who is mentally disabled, as it violated the Eight
Amendment’s restrictions on cruel and unusual punishment. However, it allowed
the states some flexibility on how they determine whether someone was mentally disabled.
Nine states (including Florida and Idaho) use an IQ score of 70 as a cutoff for
a mental disability. They deem anyone who scores above a 70 as competent. At
the heart of this case is whether using a 70 IQ score cutoff standard violates
the 2002 decision, as it is too inflexible and does not allow the consideration
of other factors, such as social and practical skills, and years of mental
incompetence.

The case before the Supreme Court involves Freddie Lee Hall,
a man who was convicted and sentenced to death for sexually assaulting and
murdering a woman who was 7 months pregnant. In 1999, the Florida court
ruled that he was mentally disabled but he would still have to face the death
penalty. After the 2002 Supreme Court ruling, he challenged his death penalty
case, arguing he should not be executed because the state deemed he was
mentally disabled. However, Florida subsequently changed how it determined
whether someone was mentally disabled after the 2002 decision, setting the 70
IQ standard.

The state of Florida is now claiming Hall is not mentally disabled
but he continues to claim that he is. Hall has taken several IQ tests, all of which
have put his IQ slightly over 70. His lawyers are arguing that existing IQ tests
cannot measure IQ in a reliable way, as scores can change from test to test. His
scores include 71, 73, and 80. His lawyers argue that Hall is clearly mentally disabled
based on his low IQ and other measures, such as brain damage and psychological
problems. They argue that the court should take all of these factors into
consideration when determining whether someone is competent.

This case is interesting from a research perspective as it
deals with how social scientists measure abstract concepts that they cannot
precisely define or measure. Psychologists have a good idea of what being
mentally disabled means, but they have not identified factors that are precise
enough to have a specific operational definition. Nevertheless, IQ tests are
still a good partial measure of mental competency, even if they are imperfect.

Although it is likely that after this case is decided, the
Supreme Court will continue to allow states to use IQ tests as measures of
competency, the Supreme Court may change how states can use IQ scores as
a measurement tool. Since IQ scores vary from test to test, perhaps the Supreme
Court will require that states administer multiple tests. In addition, perhaps
the court will rule that states should use a 95% confidence interval to measure IQ
instead of a point estimate. So, for example, if someone’s IQ score is 74 +/- 5
points, it is possible that his true IQ is below 70, making them mentally
disabled. The Florida Supreme Court ruled that the 2002 ruling does not require
states to take into an IQ score range, just the point estimate, so the Supreme
Court has the opportunity to be more specific and require a confidence interval (as the 2002 ruling suggested that "mild mental retardation is typically used to describe people with an IQ level of 50—55 to approximately 70").

Julie VanDusky-Allen

About Julie VanDusky-Allen

Julie VanDusky-Allen is at Boise State University and received her PhD in Political Science from Binghamton University in 2011. Her research focuses on institutional choice and development, political parties, the legislative process, and Latin American politics.

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