[cvoss]

You may be referring to the court's (and other appellate courts') long-standing practice of not second guessing a trial court's finding of what did or didn't happen, unless a "clear error" is demonstrated to have been committed by the trial court.

SCOTUS decisions and opinions, therefore, should not be construed as to concur with the trial court about what actually happened. They take it as granted that those things occurred, and provide the best legal resolution they can under those assumptions. The cases they hear aren't about determining "who did what". That's done and settled usually. They are about "what now?"

[UncleMeat]

There's more to it than that.

Gorsuch mixing up nitrous oxide and nitrogen oxide over and over is a recent fun example. The court also has engaged in fact finding despite the rules. Kennedy v Bremerton is one example. Alexander v. South Carolina State Conference of the NAACP is another.

You also see absolute garbage lies. FEC v. Ted Cruz for Senate has the majority saying "we can't find examples of X happening" while the dissent has a big list of examples of X happening. Or just straight up falsehoods about original understanding. DC v. Heller is a great example of this.

[vundercind]

I mean that they make errors in statement of fact supporting their rulings and, worse, incorporate those facts into their ruling in material ways.

Say the Supreme Court majority writes, as guidance to lower courts, that interpretation of a certain amendment should feature consideration of laws enacted early in the country’s history, and before its founding. They further write that for the specific question before them, the total absence of similar laws in that history means they must rule a certain law unconstitutional.

Further suppose they were simply factually incorrect to the point that such laws were in fact common and are very easy to find, if you look like at all.

Now what? If you apply their guidance on how to analyze these questions, you’d have to reverse their ruling on laws similar to the one they struck down, should they come before you. But they ruled that specific one unconstitutional… but their ruling was contrary to the guidance they gave.

So we end up tied in a bit of a knot. Had these facts been argued rather than pulled out of some damn amicus brief without examination, perhaps the government would have presented a large pile of examples to rebut the simply-false claim that no similar laws existed in the country’s early history. But the court injected these “facts” as a key part of their reasoning when writing their decision, instead. Would it have changed the outcome? No. Would it, perhaps, have made it too embarrassing even for these clowns, to include that particular bit in their ruling? Maybe! And future lower court cases might take a different course, as a result.

[EDIT] The take-away for the casual reader of Supreme Court opinions, then, is that if they write something like "no examples of such laws exist until [YEAR]" don't be surprised if that turns out to be hilariously wrong. A "fact" making it into a Supreme Court opinion is not a strong indication the fact is... an actual fact. Their opinions are far less well-researched than one might suppose, emphasis on far, it's not that they're just imperfect like any people, their fact checking is outright poor by any standards.

[hnfong]

I think you're using too many suppositions.

Do you have an actual example? Or two since you're using plurals?

[vundercind]

My specific example is just Bruen with the serial numbers filed off.

Factual errors are downright common (a Google will turn up many efforts at fact-checking the "facts" in Supreme Court opinions) and aren't a new problem, dating back basically forever.

One key problem is that they simply don't have the resources to check all their facts. Their sources of facts are often amicus briefs from interest groups and specialized court-lobbyists, drawn from large piles and quickly skimmed for relevance by overworked early-20s law clerks. It would be surprising if they didn't get things wrong all the time. They do—luckily, a lot of times, it barely matters, but sometimes they get facts wrong that were central to their opinion.

The point is, don't believe a "fact" you read in a court opinion without double-checking. Even if it's about legal history.

[EDIT] As my sibling commenter points out, it's also the case that sometimes they just lie on purpose. But even absent that, the circumstances under which opinions are written would generate factual errors by accident, with some frequency.

[UncleMeat]

FEC v. Ted Cruz for Senate is a great example of a case where the majority says "we don't see examples of X" while the dissent cites a big list of X.

Heller is also a famous case where basically every historian (as well as the defense) points out clearly that Scalia's interpretation just isn't the original understanding of the text.

[paulryanrogers]

Won't someone think of the bump stock manufacturers?!

[vundercind]

I was making a barely-veiled reference to Bruen, actually. "Can cities require demonstration of need, to carry firearms?"

The bump stock ruling's stupidity had more to do with resting entirely on silly, plainly-motivated reasoning than its relying on objectively wrong "facts".

Incidentally, I was wrong about it mattering whether it was argued: the historical evidence was argued, and the majority simply went "uhhhh those many examples don't count, because I don't want them to". What's been turned up since the case is examples that fit the much narrower criteria they said would have been needed (neatly carved out to evade the provided examples) but positively asserted don't exist (to any notable degree), in such volume that it's beyond clear that restricting carry of firearms in towns on a need-basis was common throughout the country's history, and not just in the West (their reasoning for rejecting those examples, I shit you not, was "um, those don't count because they're from one area, never mind it's a giant area"—if it's starting to look like they were playing Calvinball with that ruling, it's because that's exactly what they were doing)