youthful offender

or youth of·fend·er

[yooth-fuh l uh-fen-der or yooth uh-fen-der]
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noun
  1. a young delinquent, especially a first offender, usually from 14 to 21 years old, whom the court tries to correct and guide rather than to punish as a criminal.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018