Background: In Austria, mentally ill perpetrators not guilty for reasons of insanity are committed into a custodial measure to receive treatment. The rate of these detainees returning after their conditional release because of reoffending or revocation decreased significantly over a period of 15 years. Aims: This study aims at examining this system and the adjustments made over a period of 10 years, in order to identify changes responsible for the observable decline of the recidivism rate. Method: Therefore, a quantitative study of 807 prison and court files was conducted, extracting information concerning former detainees either released in 2001 & 2002 (n ¼ 67) or 2011 & 2012 (n ¼ 134) and subsequently comparing the groups. Additionally, expert interviews were conducted. Results: As one major change, the data revealed improvements regarding the preparation and management of the time on parole. The possibility for detainees to test their readiness for life outside the confinement through temporary interruptions of custody was enhanced, as were post-This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.