NCPA - National Center for Policy Analysis


October 25, 2004

Research shows that the adolescent brain continues to develop up until the age of 25, prompting some legal experts to argue that teens who commit crimes should not be subject to capital punishment.

Researchers from the National Institute of Mental Health tracked the brain development through magnetic resonance imaging of 13 individuals between ages 4 and 21:

  • During the teen years, the brain's "gray matter" is pruned by about 1 percent per year, being replaced by "white matter," which are neuron projections covered in a protective sheath.
  • The frontal lobe, which controls impulse behavior, does not fully mature until about 17 years of age.

In other words, the frontal lobe takes control over emotional responses -- it keeps an individual from "killing someone" when they are insulted in a social situation.

Moreover, Dr. Abigail Baird of Harvard Medical School notes that teens have difficulty assessing future consequences of their behavior due to their lack of experiences they can mentally process. While adolescents may score well on tests, this can be mistaken for a sign of maturity.

Most scientists are hesitant to translate adolescent brain development research into sweeping punishment standards for teen criminals. However, the Supreme Court will hear a case in October involving a 17-year-old who committed murder. Defense attorneys hope to compare juvenile brain development with mental retardation, thereby exempting him from the death penalty.

Source: Mary Beckman, "Crime, Culpability, and the Adolescent Brain," Science, July 30, 2004; and Jules Asher, "Imaging Study Shows Brain Maturing," National Institute of Mental Health, May 17, 2004.

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