I was especially pleased to see that the Times editorial focused on the very simple principle that is at the heart of the matter:

The essence of the American criminal justice system is reactive, not predictive: You are punished for the crime you committed. You can’t be punished simply because you might commit one someday. You certainly can’t be held indefinitely to prevent that possibility.

Or, as the court in Minnesota put it:

It is fundamental to our notions of a free society that we do not imprison citizens because we fear that they might commit a crime in the future. Although the public might be safer if the government, using the latest “scientific” methods of predicting human behavior, locked up potential murderers, rapists, robbers, and, of course, sex offenders, our system of justice, enshrined in rights guaranteed by our Constitution, prohibits the imposition of preventive detention except in very limited circumstances. This strikes at the very heart of what it means to be a free society where liberty is a primary value of our heritage.

Defenders of these laws often point to the exceptionally high recidivism rate for sex offenders as a way of justifying these post-conviction prohibitions. Why, even the Supreme Court has said that the risk of recidivism for sex offenders is “frightening and high” — “estimated to be as high as 80%.”  See McKune v. Lile, 536 U.S. 24, 33 (2002) and Smith v. Doe, 538 U.S. 84 (2003).

But as Professor Ira Ellman demonstrates in his outstanding analysis at casetext.com (“The Supreme Court’s Crucial Mistake About Sex Crime Statistics“), it’s all pretty much nonsense:

[The Court] had just one citation for its much-quoted statement: a 1988 Justice Department “Practitioner’s Manual”. That reference likely came from the amicus brief supporting Kansas filed by the Solicitor General, then Ted Olson, which also cites it. The Practitioner’s Guide itself provides but one source for the claim, but it’s no scientific study. It’s a 1986 article from Psychology Today, a mass market magazine aimed at a lay audience, which had this sentence: “Most untreated sex offenders released from prison go on to commit more offenses–indeed, as many as 80% do.” Freeman-Longo, R., & Wall, R, Changing a lifetime of sexual crime, Psychology Today (1986). That sentence is a bare assertion with no supporting reference. Nor did its author have the scientific credentials needed to qualify at trial as an expert on recidivism.  He was a counselor, not a scholar, and the article containing the sentence isn’t [even] about recidivism statistics. It’s about a counseling program for sex offenders he then ran in an Oregon prison. His unsupported assertion about the recidivism rate for untreated sex offenders was offered to contrast with his equally unsupported assertion about the lower recidivism rate for those who complete his program.

It appears to be an unfortunate, but crystal-clear, illustration of the cognitive bias that leads people — even Supreme Court justices — to believe statements that confirm preconceived beliefs without demanding any actual evidence in support. What the court really should have said — the only statement that would have been consistent with the facts before it — was:

“The author of some article published in Psychology Today thinks that the recidivism rate is frightening and high, possibly as high as 80%.”

Not quite as impressive that way, and an awfully thin reed on which to rest the crushing burdens that these prohibitions and restrictions impose.

The actual data, from actual studies, tell a very different story, as Ellman’s careful analysis demonstrates quite well. As usual, it’s a more complicated story than any single sentence can capture, so I’ll let you have a look at it yourself if you’re interested.