The Supreme Court sided in separate cases with a Black Lives Matter activist and a Texas prison inmate Monday, and new justice Amy Coney Barrett became the court’s first member to make her debut via telephone.

Chief Justice John G. Roberts Jr. welcomed the 48-year-old Barrett to her lifetime appointment with a wish for a “long and happy career in our common calling.” The court last met in person to do its work in March — it has been holding arguments by teleconference since May because of the threat of the coronavirus.

Barrett, a University of Notre Dame law professor who served for three years on the U.S. Court of Appeals for the 7th Circuit, sounded confident and well-versed in the details of the technical cases before the court.

One involved whether government documents involving regulation for cooling water intake structures may be kept from an environmental group, and another concerned benefits decisions by the U.S. Railroad Retirement Board.

“So, in thinking about the 231g question and whether the denial of a motion to reopen determines rights or liabilities, I think when you look at 261.2 . . .” is how Barrett opened her questioning in Salinas v. U.S. Railroad Retirement Board.

Barrett knows well that the Supreme Court’s docket ranges from the monumental to the mundane. She was a clerk to Justice Antonin Scalia and is the fourth consecutive new justice to have worked there as a law clerk.

Barrett, who began work less than a week ago, did not take part in the two opinions the court handed down Monday, each vacating a decision of the U.S. Court of Appeals for the 5th Circuit.

In one, the appeals court had said Black Lives Matter activist DeRay Mckesson could be sued by a police officer who was injured in a 2016 protest in Louisiana.

Mckesson organized the demonstration after the death of Alton Sterling, a Black man who was fatally shot by police after a struggle outside a convenience store, an incident caught on video.

At the Baton Rouge protest, a police officer identified in court papers only as John Doe was struck by a projectile thrown by someone in the crowd. The officer suffered serious injuries, including to his brain.

He sued Mckesson, even though he did not accuse the activist of throwing the “rock-like” object or even knowing who did. The officer alleged Mckesson was liable because he should have known violence would result because of the protest.

A federal district judge threw out the lawsuit, but a panel of the 5th Circuit reinstated it. The entire circuit reviewed the decision, and the lawsuit was allowed to proceed after a split decision.

Civil rights groups and First Amendment activists were alarmed by the appeals court’s decision and said it conflicted with a 1982 Supreme Court decision, NAACP v. Claiborne Hardware Co., which limited liability for protests.

The NAACP filed a friend-of-the-court brief after the American Civil Liberties Union brought Mckesson’s case to the Supreme Court.

The justices sidestepped the First Amendment question. In an unsigned opinion, the court said the 5th Circuit should have asked the Louisiana Supreme Court whether damages were even available under state law before proceeding to the First Amendment questions and sent the case back for that to happen.

Vera Eidelman, staff attorney with the ACLU Speech, Privacy and Technology Project, said the high court did the right thing.

“Protesters cannot be held liable for the unlawful acts of others that they did not direct, order, or incite simply because they were at the same protest,” Eidelman said in a statement. “We are gratified the Supreme Court has recognized there are important First Amendment issues at stake and has asked the state courts to review whether their law even permits such a suit.”

The organization also released a statement from Mckesson: “Today’s decision recognizes that holding me liable for organizing a protest because an unidentifiable person threw a rock raises First Amendment concerns. I’m gratified that the Supreme Court vacated the ruling below, but amazingly, the fight is not over.”

Justice Clarence Thomas dissented from the court’s action in Mckesson v. Doe but did not provide specifics for his disagreement.

In a second case, the justices said Texas inmate Trent Taylor could proceed with his lawsuit against correctional officers whom he accused of detaining him for six days in 2013 in a pair of “shockingly unsanitary cells.”

The first cell was covered in feces, Taylor alleges. “Fearing his food and water would be contaminated, Taylor did not eat or drink for nearly four days,” the court wrote.

He then was moved to a cell where a clogged drain caused raw sewage to spill across the floor, Taylor said. “Because Taylor was confined without clothing, he was left to sleep naked in sewage,” the court wrote in the unsigned opinion.

A 5th Circuit panel agreed the conditions violated the Constitution. But because there was no clear precedent regarding keeping an inmate in such conditions for “only six days,” the panel awarded the officers qualified immunity for their actions. That means they did not have “fair warning” that their specific acts were unconstitutional.

That was a mistake, the Supreme Court said. “No reasonable correctional officer could have concluded that, under the extreme circumstances of this case, it was constitutionally permissible to house Taylor in such deplorably unsanitary conditions for such an extended period of time,” the court wrote.

Again, Thomas dissented without comment. Justice Samuel A. Alito Jr. said the court should not have taken up the fact-specific case.

“Every year, the courts of appeals decide hundreds if not thousands of cases in which it is debatable whether the evidence in a summary judgment record is just enough or not quite enough to carry the case to trial,” Alito wrote. “If we began to review these decisions we would be swamped, and as a rule we do not do so.”

But since the court took up the case, Alito said, “I agree that summary judgment should not have been awarded on the issue of qualified immunity.”

The case is Taylor v. Roijas.