Justice Alito’s opinion in Williams v. Illinois cites an old English case:

Recognizing that Lambatos’ testimony would carryweight only if the underlying premises could be established, the judge noted that “the issue is . . . what weightdo you give the test [performed by Lambatos], not do youexclude it.” Id., at 94. This echoes the old statement in Beckwith that an expert’s opinion based on disputed premises “might not go for much; but still it [is] admissible evidence.” 1 Camp., at 117, 170 Eng. Rep., at 897.

Justice Thomas, in his concurring opinion, says wait, not so fast.

2In its discussion of history, the plurality relies on Beckwith v. Sydebotham, 1 Camp. 116, 170 Eng. Rep. 897 (K. B. 1807). In that case, experts were asked to render opinions on a ship’s seaworthiness based on facts read into court from the sworn ex parte deposition of a witness who purported to have seen the ship’s deficiencies. To be sure, Beckwith involved expert reliance on testimonial hearsay. But Beckwith was an English case decided after the ratification of the Confrontation Clause, and this form of expert testimony does not appear tohave been a common feature of early American evidentiary practice. See 29 Wright §6271, at 300–301; 1 Broun §14, at 86–87; Kaye §4.6, at156–157.

Oh snap. Post-enactment history from another country is not evidence of what the Confrontation Clause meant at the time of its ratification.

But wait, you say? Time of the ratification of the Confrontation Clause? This case does not involve the federal government–against whom the 1791 Confrontation Clause applies. Rather, it involves Illinois, against whom the 1868 Confrontation Clause applies, as incorporated through the Fourteenth Amendment.

But wait, I remind you. The court rejected this originalist reading of the Fourteenth Amendment in McDonald. So Justice Thomas correctly applied the Court’s flawed incorporation doctrine here. Even though his opinion in McDonald went the other way.