Assessing the risk of future offending is an evolving science. We currently can assess such risk only in persons already convicted of a violent crime. We are specifically predicting the risk of re-offense or recidivism. Such predictions include the risk of further sexual offenses, nonsexual violent offenses, nonviolent criminal offenses and noncriminal technical violations of conditions of release. Technical violations are the most common with about half of all types of offenders having such issues.
Some sex offenders have many victims before they are apprehended. Others offend only once. Once someone has been arrested for a sexual offense their likelihood of continued sexual offending is actually much lower than is commonly believed. Homicide has the lowest rate of continued offending, followed by sexual offending. Simple assault, burglary and drug crimes have the highest re-offense rates. Among sex offenders who do recidivate, further sexual offenses are the least common reason for re-arrest with about 15% (studies vary) being arrested for new charges once released to the community.
The issue is to distinguish between offenders who are more likely to re-offend than other offenders. Among offenders classified as the lowest risk of re-offense, fewer than 5% re-offend. Among those predicted as high-risk of re-offending half will be re-arrested within five years and almost all will be re-arrested within ten years. The longer a person successfully resides in the community without offending the less and less likely it is they will re-offend.
While risk prediction models are not infallible they show significantly greater accuracy in risk prediction than does common sense or professional judgment alone without the use of the risk prediction models. Simple gut feeling or professional instincts are inaccurate, worse than flipping a coin. Scientifically developed risk prediction models are 70 -80% accurate.
Some believe that incarceration helps lower recidivism. In fact, offenders who are incarcerated have more difficulty conforming after release than do similar offenders who were sentenced to probation. Many offenders can be successfully supervised in the community while participating in outpatient sex offender rehabilitation. Incarceration seems warranted only when there is a high likelihood of further offending.