While it remains impossible to determine exactly whether a sex offender will re offend statistically there are underlying factors that point to the sex offenders risk profile in relation to re offending (or recidivism).
North Carolina State uses a form (static-99) to assist in trying to determine the risk profile of a male sex offender. This is a form that originated in Canada and the questionnaire is fairly standardised. The form is also used widely in The U.S. and Europe. The risk level determined correlates to the monitoring and supervision post release or while on probation.
No relevant assessment is applied to female sex offenders due to negligible numbers. There are also very few studies in to recidivism for females again due to numbers. However a system that has been developed in Iowa has been tested in N.C. Dept. of Corrections in relation to female sex offenders.
There are ten questions to The Static-99 form. The form is administered by correction or probation officers post conviction or prior to release.
Those factors taken in to consideration are age at release, criminal background incl. Sex offenses, relationship history, also whether the victims were related at all, male or strangers. All of these factors, in studies, have pointed to increased risks of re-offending. As an example an older offender is less likely to re-offend. Sex offenders whose victims were male, statistically, are more liable to re-offending.
Risk factors carry a score from 0>3 and total thereof. 6 or over confirms an offender is at high risk to re-offend. 0>1 places the offender at low risk. It is worth noting that the Static-99 is not used for all sex offending cases. The form is not used in cases for statutory rape and/or child pornography.
It is also worth mentioning that the developers concede Static-99 lacks accuracy in confirming numerical estimates in relation to risk of sexual re offending for any specific sex offender. These findings were published in Criminal Justice and Behavior.