Chief Justice John Roberts Jr. rarely loses his temper.

Since his days as a top Supreme Court advocate in the 1990s and early 2000s, he has been known as a calm, even-tempered voice at the court. Asked in 2000 why he was not more impassioned in his delivery, he told this reporter, “Impassioned rhetoric doesn't work with the Supreme Court. If it did, I'd become impassioned.”

Now in his thirteenth year as chief justice, Roberts has mostly kept that reputation.

Which is why it was so unusual that Roberts seemed to get heated February 20 during an otherwise sedate oral argument in City of Hays, Kansas v. Vogt. The case asked whether the Fifth Amendment's protection against forced self-incrimination extends to statements introduced in pretrial probable cause hearings.

But Roberts didn't get riled up over the merits of the case. Roberts is a stickler for procedure, and the episode shows that he is more prone to flare up when rules and traditions are sidestepped than anything else. The last time Roberts seemed this upset may have been in 2016, when he scolded a lawyer for expanding the scope of a case beyond the issue the court agreed to resolve.

Listen to the full exchange here:

[falcon-embed src="embed_1"]

Well into the Vogt argument last week, Justice Stephen Breyer was trying to figure out from the record whether in fact defendant Matthew Vogt had incriminated himself in pretrial proceedings and whether his lawyer objected. “Looking at the transcript of the preliminary hearing,” Breyer said, “I couldn't find any instance where any of the compelled statements were introduced into the preliminary hearing.”

Vogt's lawyer Kelsi Corkran, partner at Orrick, Herrington & Sutcliffe, replied that “none of that is in the record,” and was about to explain why.

But Roberts did not wait for an explanation. He was upset. “That's an important point, isn't it?” he said. “Well, before we start having an extended exchange about … something that's not in the record, I — well, I guess I would just like to point out that it's not in the record. There's a reason we confine things to what's in the record, including, 'how do we know what this is if it's not in the record?'”

Corkran, who was arguing her first case before the high court, tried to interject, but Roberts wasn't finished. “How do we know that it's been adequately — had a chance for people to object to it and all that?” He asked. “It's not just a passing comment that it's not in the record.”

As he continued, Roberts seemed angry that Breyer had asked the question: “As far as I'm concerned, coming in and saying I want to know about this thing that's not in the record is no different from somebody else coming off the street and saying: 'Hey, wait a minute, I know what happened in this case.'”

Roberts calmed down only slightly when he told Corkran, “Go ahead and answer it. It's a question that you've been presented with. Go ahead and answer it.”

Perhaps trying to shield Corkran from the chief's ire, Breyer said, “You don't have to answer it.”

Roberts was still steaming. “No, No, no, feel free. I'm just saying I will discount the answers because it's not something that's in the record.”

Unruffled by Roberts' snit, Corkran calmly seized the moment, answering in a way that may help her client: “It's really important to explain that the reason it's not in the record is because petitioner chose to seek this court's interlocutory review at the pleading stage.”

She went on to suggest, “If this court wanted to [dismiss] the case as improvidently granted, we would certainly not object.” Such a dismissal would leave in place a ruling by the U.S. Court of Appeals for the Tenth Circuit that favored her client.