What is the minimum age under which a person cannot be punished by death for an offense?

The minimum age for which a person cannot receive the death penalty for an offense is 18 years old. This is rooted in both legal and human rights considerations, reflecting the understanding that individuals under this age are generally considered to lack the full capacity for judgment and understanding of the moral implications of their actions. The U.S. Supreme Court has ruled in cases such as Roper v. Simmons (2005) that executing individuals under 18 is unconstitutional, as it violates the Eighth Amendment's prohibition against cruel and unusual punishment. This standard aims to recognize the developmental differences in minors compared to adults, ensuring that they are treated fairly within the criminal justice system.