In a 5-3 decision issued on March 28, the Supreme Court vacated the death penalty conviction of Bobby James Moore after a Texas court ruled that Moore was not intellectually disabled and was subject to the death penalty. It held that the Texas court applied the incorrect standard to determine intellectual disability by relying solely on Moore's IQ score of 74. Instead, the Texas court should have considered the standard error of measurement showing how much the score could range around Moore's "true" IQ score. Moore's IQ ranged from 69 to 79. Under Supreme Court precedent, "where an IQ score is close to, but above, 70, courts must account for the test's 'standard error of measurement.'"
The Texas court also erred by heavily relying on Moore's perceived adaptive strengths (he "lived on the streets, mowed lawns, and played pool for money") instead of his adaptive deficits, which the medical community focuses on when conducting the adaptive-functioning inquiry. The Texas court also erred by relying on "evidentiary factors" from the Texas case Ex parte Briseno, which the Supreme Court determined was "untied to any acknowledged source" in medicine or law. As a result, the conviction could not stand.
For more opinion analysis, see this SCOTUSblog post.