Zero tolerance also allows for a sound rehabilitative role  A custodial sentence, particularly for juveniles, takes them out of the atmosphere (often surrounded by drug use and living in poverty and or abusive homes) that encourages criminality. Rehabilitation through the prison system is not just a possibility but a central tenet of many penal codes. Education and discipline are both vital to our prisons. The large number of police on the ground also allows for a supervisory role in the community after the prisoner is released to reduce re-offending.  The earlier on in the chain of criminality that people are given help, the greater chance there is of success that a cycle of re-offending will not develop. [1]  [1] Petersila, Joan, ‘When Prisoners Return to the Community: Political, Economic, and Social Consequences’, Sentencing &amp; Corrections, No.9, November 2000, www.ncjrs.gov/pdffiles1/nij/184253.pdf , accessed 20 September 2011