In 2002, the US Supreme Court ruled that executing people with
an intellectual disability was a “cruel and unusual punishment”,
and therefore unconstitutional. For someone to be classed as
“intellectually disabled”, they have to demonstrate “significant
limitations” in their mental abilities, like problems with
literacy or social skills. These problems must also be present
before the age of 18. This all usually amounts to an IQ of 70 or
below. What the Supreme Court didn’t specify was how a
prisoner’s IQ was to be measured, and therein lies the trouble
with the ruling. There are two worrisome problems with IQ
testing. The first is that there is a margin of error when
testing a person’s IQ. An IQ score is not a precise measurement,
but should be interpreted as lying within a range. A prisoner’s
performance could vary from day to day depending on his mood or
health, and could dangerously hover around the score of 70 that
has been chosen as the cut-off. The second problem is what’s
known as the Flynn Effect – Ja