Should Supreme Court justices Google? "That Arizona contradicts federal law by enforcing applications of federal immigration law that the president declines to enforce boggles the mind," Scalia said in reading part of his dissent from the bench. If the framers had proposed that all immigration decisions will be made by the federal government and "enforced only to the extent the president deems appropriate," Scalia thundered, "the delegates to the Grand Convention would have rushed to the exits from Independence Hall." For our purposes, let's leave aside Scalia's excoriation from the left and defense from the right and focus on a different lesson: Supreme Court justices Google just like the rest of us. Scalia cited a nine-day-old newspaper article in his dissent, and he is hardly alone: The justices routinely supplement their arguments with facts, studies, media reports, law review articles and other materials that none of the parties in the case before them ever put forward or countered. How judges use generalized facts about the world in their legal decisions has become a new focus of legal academic research. Well known is the story of Justice Harry Blackmun hunkering down in the medical library of the Mayo Clinic to research abortion procedures before he wrote the 1973 majority opinion in Roe v. Wade. But there's been an information revolution since then. Now the justices (and their clerks and their librarians) are flooded with information literally at their fingertips. Social science studies, raw statistics, and other data are all just a Google search away," writes Allison Orr Larsen, a professor at William & Mary Law School. "If the justices want more empirical support for a factual dimension of their argument, they can find it easily and without the help of anyone outside of the Supreme Court building," she wrote. Larsen, a former clerk to retired Justice David Souter, studied 15 years of Supreme Court decisions for her paper. She found more than 100 examples of asserted facts from authorities never mentioned in any of the briefs in the case. And in the 120 cases from 2000 to 2010 rated the most salient - judged largely by whether they appeared on the front pages of newspapers - nearly 60 percent of them contained facts researched in-house. "Virtually all of the justices do it regardless of whether they are traditionally labeled liberal or conservative," Larsen found, "and they cite authorities they find themselves on a wide range of subject matter (from biology to history to golf)." A 2011 decision in which the court found a California law forbidding the sale of violent video games to minors violated the First Amendment provided a good example. Justice Stephen G. Breyer in a dissent provided 13 pages of studies on the topic of psychological harm from playing violent video games. Justice Clarence Thomas cited 59 sources to support his view that the Founding Fathers believed that parents had absolute control over their children's development; 57 of them were not in the briefs submitted in the case. And Justice Samuel A. Alito Jr., another dissenter, listed references to SlashGear and other Web sites to bolster his point about the "astounding violence" in the games. That prompted Scalia, who wrote the majority opinion, to criticize Alito for his "considerable independent research." There are no rules about in-house research, and Larsen is troubled by the risks: "the possibility of mistake, unfairness to the parties, and judicial enshrinement of biased data which can now be quickly posted to the world by anyone without cost." She does not claim that it has changed the outcome of a case, but she notes that inaccurate information has found its way into opinions, in part, she argues, because no lawyer for the other side knew about it or had a chance to challenge it. In Graham v. Florida, for instance, the court invalidated life-without-parole sentences for juveniles who commit non-homicide offenses. Justice Anthony M. Kennedy relied on a letter from the Bureau of Prisons, solicited at his request by the Supreme Court library, about the number of such prisoners. After the decision, the government submitted a letter to the court saying the bureau had been wrong: None of the six inmates listed in the BOP's letter was actually serving a life sentence for a crime committed as a juvenile. Do I think that factual information would have changed Justice Kennedy's mind? Larsen asked. Probably not. But she says the practice undermines the adversary process. Asked whether she had engaged in in-house fact-finding as a clerk to Souter, she laughed and declined to comment. But she added: I will tell you Justice Souter didn't own a computer. For previous High Court columns, go to washingtonpost.com/fedpage.