I previously blogged about the Court’s attempts in Sykes v. United States to rely on statistical evidence to determine whether fleeing the police by automobile was “dangerous” for the purposes of the Armed Career Criminal Act. Both Justice Kennedy in the majority, and Justice Kagan in dissent, relied on “common sense” to support their adoption of this data, even though none of it was introduced at the trial level.

Justice Kennedy noted that “although statistics are not dispositive, here they confirm the commonsense conclusion that Indiana’s vehicular flight crime is a violent felony.” Justice Thomas wrote that “common experience and statistical evidence confirm the “potential risk” of intentional vehicular flight.”  Justice Kagan found that the data was inconclusive, but noted the “majority’s intuition that dangerous flights outstrip mere failures to stop—that the aggravated form of the activity is also the ordinary form—seems consistent with common sense and experience.”

Here, we have 8 Justices who have different views about statistical data supporting social costs from vehicular flight, but in large part due to “commonsense conclusions,” “common experience,” “intuition” and “common sense and experience,” they agree on the outcome. None of these statistics were even introduced at trial, or admitted into evidence. Should courts be able to take judicial notice of these statistics because they conform to common sense?

In J.D.B. v. North Carolina, Justice Sotomayor also relied on “common sense” in her reliance on empirical studies.

Describing no one child in particular, these observations restate what “any parent knows”—indeed, what any person knows—about children generally. Roper, 543 U. S., at 569.5

5 Although citation to social science and cognitive science authorities is unnecessary to establish these commonsense propositions, the literature confirms what experience bears out. See, e.g., Graham v. Florida, 560 U. S. ___, ___ (2010) (slip op., at 17) (“[D]evelopments in psychology and brain science continue to show fundamental differences between juvenile and adult minds”).

Sotomayor’s opinion heavily relied on empirical data to make her conclusion.

That risk is all the more troubling—and recent studies suggest, all the more acute—when the subject of custodial interrogation is a juvenile. See Brief for Center on Wrongful Convictions of Youth et al. as Amici Curiae 21–22 (collecting empirical studies that “illustrate the heightened risk of false confes- sions from youth”).

In the same vein, the State and its amici protest that the “effect of . . . age on [the] perception of custody is internal,” Brief for Respondent 20, or “psychological,” U. S. Brief 21

These statistics were not introduced at trial, and were not admitted through an adversarial process. As I asked in my previous post:

What is the proper role for courts to consider statistics and common sense to illustrate social costs, such as dangers from vehicular flight?