The state Supreme Judicial Court sat Tuesday for the first time since June, and it was clear from the outset that something was different.

“Yes, it is a new look SJC,’’ Chief Justice Ralph D. Gants told those in the gallery at the John Adams Courthouse in Pemberton Square.

To his far right sat recently appointed Justice David A. Lowy. And to Gants’ far left sat Justices Frank M. Gaziano and Kimberly S. Budd — three new SJC jurists sitting together for the first time, in a historic remake of Massachusetts’s highest court.

They were nominated by Governor Charlie Baker to fill seats vacated by Justices Francis X. Spina, Robert J. Cordy, and Fernande R.V. Duffly, after their recent retirements, and they were unanimously confirmed by the Governor’s Council last month — just in time for the start of the court’s annual session.

“This is what we call in the law ‘Opening Day,’ and I want to welcome the staff and the new law clerks, as well as the new justices,’’ Gants said. “When I came on board seven years ago, (then-Chief Justice Margaret Marshall) said that each new justice changes the court, and no doubt three new justices change the court. We are blessed with three very fine justices.’’

The three new justices arrive at a time when the court will be exploring new law, with the evolution of social media and technology, and Baker’s ability to name three justices at once cements his imprint on the court’s philosophy for years to come. The justices, all former prosecutors, are relatively young and years away from the court’s mandatory retirement age of 70.

Baker could also appoint two new judges after the anticipated retirements of Justices Margot Botsford and Geraldine S. Hines in the next year, giving him an opportunity to name a majority of the seven-member court in his first term in office.

The court, the oldest continuously operating appellate court in the Western Hemisphere, hears appeals on a broad range of criminal and civil cases, starting in September and ending in May.

A single justice holds sessions each week, on a rotating schedule, to hear certain immediate motions, such as those related to trials or bail reviews.

The seven justices sit as a full bench the first week of each month, and issue about 200 written decisions a year.

On Tuesday, the court heard arguments in a dispute between a union and the state Department of Mental Health, and in criminal cases that raised questions of police seizures and grand jury instructions, and the new justices — all former Superior Court judges — immediately appeared at ease.

Gaziano, for instance, interrupted arguments in one case to question whether a police officer can detain someone to ask about a firearm. The case involved a defendant who was stopped by police because someone reported seeing a gun.

“A police officer can ask anything they want; the constitutional question is, can they detain to ask that question,’’ Gaziano asked.

“The panel was very respectful, thoughtful, and asked probing questions of both sides,’’ said Greg L. Johnson, the defense attorney in the case. “I’m looking forward to my next appearance before the SJC.’’

In a separate case, the justices considered whether prosecutors in a murder case should have instructed the grand jury on mitigating circumstances, such as self-defense. The case involved an 18-year-old who fatally stabbed one of several men who had attacked him after an alcohol-laden graduation party, in what his lawyer called a case of self-defense.

Gaziano was the trial judge, and recused himself from arguments. But his new colleagues peppered lawyers with questions, challenging the veracity, for instance, of the self-defense claim.

“The court in general — they were thoughtful, practical, well-prepared,’’ said Kenneth Anderson, the defense attorney in the case. “I was impressed with their preparation.’’

Anderson said the court has already ruled, in a juvenile’s case, that prosecutors have the responsibility to provide grand jurors with total instructions on mitigating circumstances. But that old court was split on whether the extra instructions should apply to adults.

“It will be interesting to see how the new judges see that,’’ he said.

Milton J. Valencia can be reached at milton.valencia-@globe.com. Follow him on Twitter @miltonvalencia.