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"Smart people (like smart lawyers) can come up with very good explanations for mistaken points of view."

- Richard P. Feynman, Physicist

"There is a danger in clarity, the danger of over looking the subtleties of truth."

-Alfred North Whitehead

November 8, 2010

Sex Offender Recidivism Base Rates

We have all heard the claim that sex offenders cannot be rehabilitated and that they all will invariably reoffend if allowed back into the community. What does the research tell us about that? What are the recidivism base rates for sex offenders? Are there differences in the recidivism base rates for offenders with different types of sex offenses or that possess different traits? As sex offenses are among the most serious offenses in our society, these are important questions for community safety reasons and the treatment of sex offenders.

There are many different studies that attempt to calculate recidivism base rates for sex offenders. A base rate is the proportion of a group of sex offenders that will reoffend within a specified period following any incarceration period (where the assumption is they are not able to re-offend—an assumption which is not always correct).

One of the largest meta-analysis studies of this topic showed the following recidivism base rates for sex offenders.[i]

Follow-up period Recidivism rate (95% CI)

5 years 13-15%

10 years 19-21%

15 years 22-26%

20 years 24-30%

The marginal increase in the recidivism rates decline over time. In other words, the longer a sex offender has gone without reoffending, the lower the chances are that he will reoffend. That conclusion seems to have face validity.

Hanson et al (2003) found that sex offenders with an adult victim have similar recidivism rates for another sex offense as sex offenders with child victims. However, sex offenders with adult victims have higher recidivism rates for other nonsexual violent offenses than child sex offenders.[ii]

Offenders that offend against different victims appear to have different base recidivism rates. Offenders who have offended against unrelated boy victims have a recidivism rate approximately 10 % greater than the average rate at a ten year follow-up period (30% compared to 20%). Offenders who have offended against unrelated girl victims have a recidivism rate approximately 8 % lower than the average rate at a ten year follow-up period (12% compared to 20%). Incest offenders have a recidivism rate approximately 10 % lower than the average rate at a ten year follow-up period (10% compared to 20%). [iii]

These researchers discuss the problem that many sexual offenses are not reported to police and that these recidivism rates include only the reported offenses. These researchers believe that the reported rates for the 20 year follow-up period under-estimate the actual recidivism rate due to unreported offenses, and the rates should be increased by “at least” 10% to 15% with a proportionate increase for the other follow-up periods.[iv]

This research also looked at the correlation between possible risk factors and sexual offense recidivism rates. Sexual interest in children as measured by a phallometric assessment was the risk factor most highly associated with increased recidivism with a correlation coefficient of .32. All of the following factors were correlated with increased recidivism rates; any deviant sexual preference, a history of prior sexual offenses, having any stranger victims, early onset, any related victims, any boy victims, diverse sexual crimes, antisocial personality, any prior criminal history, age, never married, and treatment dropout. The correlation coefficients for these factors ranged from a high of .22 to a low of .10. [v]

(It is important to note that although these correlation coefficients show a relationship between a factor and a recidivism rate, the correlation coefficients are far less than one, the highest correlation coefficient. A correlation coefficient of one is defined as the data showing that the factor and the recidivism rate kept in perfect step, and that the presence of one factor was always associated with an increase in the recidivism rate by an identical percentage.)

These researchers also concluded that several factors were not related to increased recidivism. These factors include, victim empathy, denial of sex offense, unmotivated for treatment, general psychological problems, sexually abused as a child, and degree of sexual contact. [vi]

The above-described research explains the base-rates of sex offenders, what does the research say about identifying those more likely to re-offender. We will take a look at that question in a future blog entry.



[i] Hanson, Kelly R, Kelly E. Morton, and Andrew J.R. Harris, (2003) Sexual Offender Recidivism Risk, What We Know and What We Need to Know, Ann. N.Y. Acad. Sci. 989: 154-166, page 155.

[ii] Ibid, p. 155.

[iii] Ibid. p. 156.

[iv] Ibid. p. 157.

[v] Ibid. p. 157

[vi] Ibid. p. 158.

The views expressed in this blog are solely the views of the author(s) and do not represent the views of any other public official or organization.

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