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competence, interrogation & confessions
The operative claimA substantial proportion of juveniles, especially those age 15 and younger, have impairments in adjudicative competence — the capacities to understand legal proceedings, reason about legal decisions, and assist counsel — at rates comparable to adults found incompetent to stand trial; developmental immaturity itself, apart from mental illness, can diminish trial competence.
The forensic field broadly accepts that immaturity — not just mental illness — can compromise a juvenile's competence to stand trial, and that younger adolescents are disproportionately impaired; this recognition reshaped juvenile-competence law and practice. What remains debated is how to set standards and apply them to individuals, not whether immaturity-based incompetence is real.
A population-level developmental finding from standardized competence assessments comparing adolescents and adults. Impairment is concentrated among younger adolescents (roughly 15 and under) and those with lower cognitive ability, and reflects developmental immaturity rather than only mental illness or disability. It describes group rates and the developmental basis of competence concerns — not any individual youth's competence, which requires an individualized clinical-forensic evaluation.
Grisso, T., Steinberg, L., Woolard, J., Cauffman, E., Scott, E., Graham, S., et al (2003). Juveniles' competence to stand trial: A comparison of adolescents' and adults' capacities as trial defendants. Law and Human Behavior, 27(4), 333-363.
Cross-sectional · N = 1,393 · adolescents vs. young adults
Youths aged 15 and younger more often performed at impairment levels comparable to adults found incompetent to stand trial, and adolescents more often made choices reflecting compliance with authority and psychosocial immaturity.
Bearing on this claim: MacArthur Juvenile Competence Study: juveniles 15 and under more often performed at impairment levels comparable to adults found incompetent; immaturity itself can diminish competence.
doi.org/10.1023/A:1024065015717Viljoen, J. L., & Roesch, R (2005). Competence to waive interrogation rights and adjudicative competence in adolescent defendants: Cognitive development, attorney contact, and psychological symptoms. Law and Human Behavior, 29(6), 723-742.
Cross-sectional · N = 152 · 11-17 years
Among 152 adolescent defendants aged 11-17, younger and cognitively less mature adolescents showed poorer comprehension of interrogation rights and weaker adjudicative competence; legal capacities tracked cognitive development more than psychological symptoms.
Bearing on this claim: Independent replication in 152 adolescent defendants tying weaker adjudicative competence and interrogation-rights comprehension to cognitive development.
doi.org/10.1007/s10979-005-7978-yRedlich, A. D., Silverman, M., & Steiner, H (2003). Pre-adjudicative and adjudicative competence in juveniles and young adults. Behavioral Sciences & the Law, 21(3), 393-410.
Cross-sectional · juveniles and young adults
In an independent (non-Grisso) sample, pre-adjudicative (Miranda) competence and adjudicative competence were strongly related, especially among juveniles, and age and suggestibility predicted both — independently validating the developmental competence deficit and the link between waiver competence and trial competence.
Bearing on this claim: Independent (non-Grisso) replication that adjudicative competence is diminished in juveniles and tracks age and suggestibility — a second research program supporting the developmental competence deficit.
doi.org/10.1002/bsl.5433 supporting verified sources
The magnitude of the finding rests heavily on a single (very large) landmark study; the design is observational age-comparison rather than experimental; legal standards and instruments for juvenile competence vary across jurisdictions and remain debated; samples are U.S.-based; and group rates cannot establish that a particular youth is competent or incompetent, which requires an individualized clinical-forensic evaluation.
Last reviewed June 20, 2026