In Crawford v. Marion County, Justice Stevens wrote for a 6-3 court, upholding Indiana’s voter identification law. In his dissent, Justice Souter employed his Posnerian research skills to conduct internet research that analyzed the burdens imposed by Voter ID laws. (Ironically, Posner wrote the 7th Circuit’s decision upholding the law–he did not use internet research at the time, but subsequently came to regret it). Justice Stevens responded to Souter’s extra-curricular research.

Supposition based on extensive Internet research is not an adequate substitute for admissible evidence subject to cross-examination in constitutional adjudication.

In remarks at the 7th Circuit Judicial Conference, Justice Stevens said he was aware of information outside the record, and laments that he did not look at it.

Stevens, who was joined by Chief Justice John G. Roberts Jr. and Justice Anthony M. Kennedy, mentioned a dozen times in the opinion that it was based on “the record” in the case.

“I learned a lot of things outside the record that made me very concerned about that statute,” Stevens said in the conversation with Kagan and Wood. “So I had the question: Should I rely on my own research or what’s in the record?”

“And I thought in that case I had a duty to confine myself to what the record did prove, and I thought it did not prove the plaintiffs’ case. And as a result, we ended up with a fairly unfortunate decision.”

Stevens alluded to his quandary in a footnote in the opinion: “Supposition based on extensive Internet research is not an adequate substitute for admissible evidence subject to cross-examination in constitutional adjudication.”

In the conversation, Stevens noted that dissenting justice David H. Souter did not share his reluctance.

“I thought David wrote one of his best opinions, relying partly on material that was outside the record,” Stevens said.

Kagan the justice briefly became Kagan the journalist as she asked the right follow-up question after Stevens explained his approach.

“Would you do it the same way again?” she asked.

“I think I would,” replied Stevens, who turned 96 last month and mentioned that he is writing a new book. “That’s a tough question. I really don’t know for sure.”

Stevens has previously expressed his regrets of the case (see here and here).