The correct response is:
It is considered cruel and unusual, because by the nature of their diagnosis, these individuals have a lessened ability to understand the severity of their crimes.
This principle is rooted in the Eighth Amendment of the U.S. Constitution, which prohibits cruel and unusual punishment. The U.S. Supreme Court has ruled that executing individuals with intellectual disabilities is unconstitutional due to their diminished capacity to understand and engage in the legal process, as well as their lesser culpability in relation to criminal behavior.