Over at Slate, Mark Joseph Stern has an article trying to explain the Justices’ votes in Rodriguez v. United States, yesterday’s Fourth Amendment case on the length of traffic stops. Stern focuses his attention on Chief Justice Roberts, who ruled for the defense in Rodriguez but for the government in December’s Heien v. North Carolina on reasonable mistakes of law. Stern has a theory for why the Chief Justice could have voted for the defense in one case and the government in the other.

In a single sentence, Stern notes that it’s possible that the Chief Justice simply thought the two cases presented different legal issues. But then Stern settles into his real theory: Something happened to Chief Justice Roberts between Heien in December and Rodriguez in April that fundamentally changed his view of the police. Roberts must have had an “epiphany.” And we need to figure out what caused the epiphany. Here’s Stern:

It could be that in the last few months, Roberts got pulled over—apparently for the first time in his life—and finally grasps how fraught such encounters often are.

There’s another possibility: Perhaps the savvy, media-aware Roberts has finally learned the lessons of Ferguson and is trading in his logical abstractions for some much-needed legal realism. The Justice Department’s investigation into Ferguson revealed a system of law enforcement that used police power to target minorities and trap them in a cycle of debt and incarceration. From 2012 to 2014, blacks made up 67 percent of Ferguson’s population but accounted for 85 percent of traffic stops. Even worse, blacks were twice as likely as whites to be searched during the stop—though whites were 26 percent more likely to have contraband.

Anybody who hears of these abuses—and it’s hard to imagine Roberts did not—should be able to see why the Rodriguez decision is so obviously correct. The officer held Rodriguez for eight minutes after issuing his warning, despite the fact that, in his words, “I got all the reason[s] for the stop out of the way.” He had no reason to believe Rodriguez was carrying drugs; his decision to hold him was a mere exercise in arbitrary power. Curbing cops’ ability to detain drivers on absolutely no reasonable suspicion won’t solve all the problems Ferguson exposed. But, as Roberts may have realized, it might dissuade officers inclined to use their authority to intimidate citizens out of exercising their constitutional rights.

I think Stern’s analysis tells us more about Stern’s views of the law than what the Justices think. According to Stern, the issue in Heien and Rodriguez boils down to “whether the justices really get the volatile, nerve-wracking nature of police encounters, the dramatic power imbalance that allows cops to trample on citizens’ rights.” There’s no point in analyzing the actual legal issue presented, as that answer is totally obvious. Stern only mentions the legal merits in a single dismissive sentence: “From a purely constitutional perspective, Justice Ruth Bader Ginsburg’s majority opinion [in Rodriguez] is so obviously correct that it’s a little disturbing to see only six justices endorse it.” It’s so obvious, there’s no point in even saying why.

As Stern appears to approach things, then, there are two kinds of Justices. There are those who “get it” and vote for the defense, and those who don’t “get it” and vote for the government. I gather that is why Stern needs to find some kind of outside epiphany to explain why the Chief Justice “changed” his vote. Stern seems to offer up Ferguson as the explanation only because something has to explain the switch. (The timing doesn’t really fit if you look at the dates, but that’s just a detail.) Within Stern’s framework, there has to be a non-legal explanation for voting differently in cases that present the same issue just a few months apart.

My view is very different. At one level, Heien and Rodriguez share some similarities. They are both Fourth Amendment cases about what makes a traffic stop constitutionally reasonable. But the similarities end there. Broadly speaking, Heien is about police actions that seemed lawful at the time but that were later deemed, by an appellate court, to be unlawful. It’s about legal technicalities, and whether the rule that seizures must be reasonable should incorporate the technicalities. On the other hand, Rodriguez is about how much to let the police use a stop for traffic violations as an opportunity to investigate other crimes. It’s about how much to let one police power bleed over into another police power. Existing doctrine aside, those are two pretty different questions with pretty different implications.

And it’s not just the Chief Justice who apparently thought so. Like Stern, I happen to think that the defense had the more persuasive argument in both Heien and Rodriguez. But a majority of the Justices split their vote. Remember, Heien was 8-1 for the government and Rodriguez was 6-3 for the defense. Justices Scalia, Ginsburg, Breyer, and Kagan also voted for the government in Heien and for the defense in Rodriguez. If we need an epiphany to explain the difference, then it must have been a group epiphany.

But I don’t think the results in these two cases has to be explained by what the Justices ate for breakfast or what they saw on TV. Of course, we can and must readily acknowledge the role of worldview in how Justices approach cases, whether in the Fourth Amendment context or elsewhere. Some Justices approach criminal cases more from the government’s perspective, and some approach them more from the defense perspective. No surprise there. But even within that basic framework, the most promising starting point to explain why different cases yielded such different vote counts is usually the difference in the cases themselves.