WHY DON’T SUPREME COURT JUSTICES KNOW MATH?Monday, the Supreme Court will here Hall v. Florida. The issue in the case is whether the Florida state court erred in sentencing to death a man with an IQ below the threshold for intellectual disability (IQ of 70).
In 2002, Justice John Paul Stevens wrote in Atkins, a similar case of a ‘mentally retarded’ man sentenced to death, that national consensus finds execution of an intellectually disabled criminal a violation of the Eighth Amendment’s prohibition on ‘cruel and unusual punishment.’
The IQ of Freddie Lee Hall, the defendant in Monday’s case, was measured numerous times and scored in the sixties and low seventies. The Florida state judge used the test of his IQ that put him above 70 as evidence that he does not fall under the precedent of Atkins and sentenced him to death.
This case is not the first time the Supreme Court will grapple with statistics. In Casey v. Planned Parenthood, Justice Scalia used statistically non-significant data to uphold arbitrary limits on abortion that have no founding in science (but tremendous founding in Justice Scalia’s Roman Catholic ideology).
The problem in Hall is the following:
IQ is a distribution over a Gaussian bell curve with a center value of 100 which equals average. That means the standard deviation is 15. The way you calculate the margin of error is by taking the square root of the standard deviation, which is 3.87. This number means as much as 34% of the population has an IQ within a range of 7.74 (3.87 x 2) points of what was measured. For example, if Hall scores an IQ of 73, there is a 34% chance his actual IQ would is still be below the threshold for capital punishment. Hall had numerous IQ measures that came up below 70 further suggesting his actual IQ is on the lower end of the range.
Will the Court consider this in Monday’s oral argument?