Final answer:
Individuals under 10 years of age are generally presumed to lack mens rea, though this can be challenged with evidence. Age-related legal principles affect competency to stand trial and sentencing guidelines, like those in Atkins v. Virginia.
Step-by-step explanation:
The question pertains to the age at which there is a presumption of no mens rea, meaning the mental state of understanding the wrongfulness of an act, which can be rebutted given sufficient evidence.
While different jurisdictions may have varying age thresholds, generally, individuals under 10 years of age are presumed to lack mens rea, but it can potentially be established depending on the specific circumstances, intelligence, and understanding of the individual.
This concept of age and criminal responsibility is closely tied into broader legal principles such as competency to stand trial, the imposition of the death penalty on individuals with intellectual disabilities, as in Atkins v. Virginia, and the protection from being tried twice for the same offense or being compelled to testify against oneself, as enshrined in the United States Constitution's Fifth Amendment.