And you hit the nail on the head–“would have”)—that he wrote something that would be associated with the court’s judgment is well-nigh irrelevant since he was dead.

By analogy, which votes do we count in a general election. Most states require the voter to be alive on election day, and thus if there were a ready means to cull dead absentee votes, they would.

But you go beyond election day, and jump forward to the day that the election results are verified. In the case of the presidential election, this might be the date that each state certifies the vote for the electors.
What of dead electors, expired from the time they cast their votes, until the votes are counted on the Senate floor.
By applying scrutiny too rigorously on the vitality of the voter on some later date, it gets really messy and difficult to have a clean count.
Alive on the date of voting is much more simpler to assess.

He wrote what was the majority opinion (or would have been the majority opinion if his vote were counted) which is a pretty strong indicator.

My practice when discussing some new tool of state surveillance with a person who’s in favor of it, is just to ask of, e.g., a progressive Democrat: “Would you be OK with (former) New York Mayor Giuliani’s police chief having access to this?”…for a Republican, flip it and ask the same question about, e.g., Hillary Clinton.
Often gets a thoughtful response.

But the technical step was the issue, right? A non-negotiable prerequisite to the issuance of a judgment was the affirmative vote on the date of issuance of 6 judges. When he died, Reinhardt was no longer a judge. So his vote, not happening on the date of the issuance of the decision, simply cannot count. Anything else is monkey business, and the optics are terrible.

Following the technical step ensured that the judicial power of the United States was exercised properly,. The judges that acquiesced to this seem unfit, and not just because the got it so obviously wrong–but also they should have held a hearing on the issue and (a) let both parties be heard and (b) provide, you know, actual legal reasoning for their reasoning. That’s the judicial process, and they really screwed it up.

Reinhardt’s ineligibility may be obvious as a matter of Federal law, but it’s not obvious as some sort of universal rule of judging: the South Dakota Supreme Court released 3 opinions this winter (2 in November, 1 in December) after the justice who wrote them had died, and they counted his vote in a 4th case after he died.

Indeed, in many cases it needn’t be sufficiently reliable to support a warrant. Instead the law enforcement agency, having identified the suspect through DNA similarity to siblings or cousins, pockets a coffee cup discarded by the person and obtains the DNA. In those cases, as in many, the problem with the genetic panopticon is not going to be so much inaccuracy as inescapability. Hurrah for its role in catching serial killers, not so much hurrah for the way it provides to match who attended a meeting of dissidents and left their DNA on a bottle or cup while there.

While I agree with the SC, the argument was that the opinion (drafted by the subsequently deceased) and all dissents were final before his death and that the public release several days later was merely a technical step.

But it only has to be sufficiently reliable to provide adequate cause for a warrant. With that, new samples could be obtained for actual use at trial.