Within the international community, there is a consensus against the imposition of the death penalty on individuals with mental retardation. The United States Supreme Court and several international human rights bodies have recognized that individuals with mental retardation should not be subject to the death penalty. Additionally, most countries maintain that individuals who are insane or mentally retarded are shielded from execution. However, reports of individuals with mental retardation who are facing the death penalty continue to surface.
One reason for this may be the lack of an international standard defining mental retardation. There is currently great variation between cultures in defining the level of mental functioning that constitutes retardation. Additionally, definitions of mental retardation vary widely from country to country, with some countries conflating mental illness with mental retardation and others completely excluding mental retardation from their definition. As a result, there is no way “to gauge the extent to which the widespread prohibition on the execution of the mentally retarded has in fact provided a safeguard for all those to whom it may apply in principle.”
Northwestern Journal of International Human Rights
Allison Freedman, Mental Retardation and the Death Penalty: The Need for an International Standard Defining Mental Retardation, 12 Nw. J. Hum. Rts. 1 (2014).