Why are individuals with intellectual disabilities not allowed to be sentenced to death?

Question

A. they are not over the age of 18, so they cannot understand the severity of their crimes
B. individuals with intellectual disabilities are only allowed to be sentenced to death for homicide.
C. It is considered cruel and unusual because by the nature of their diagnosis, these individuals have lessened ability to understand the severity of their crimes.
D. Roper V. Simmons found this sentencing unconstitutional

Answer 1

C. It is considered cruel and unusual because by the nature of their diagnosis, these individuals have lessened ability to understand the severity of their crimes.