Washington (CNN) As the Supreme Court rounds the final turns of the term, Justice Stephen Breyer seemed to launch a warning towards his conservative colleagues in an opinion released Monday.

Be very careful before you overturn precedent, he said.

Breyer's warnings, coupled with two unusual death penalty opinions and a rare vote from Brett Kavanaugh siding with the liberals on the bench, gave fodder to court watchers waiting anxiously to see how the court is interacting, and where the newly conservative majority is headed.

Major opinions on blockbuster cases concerning issues such as a citizenship question on the 2020 census and the future of extreme partisan gerrymandering are still outstanding, but Monday offered interesting tea leaves several weeks before the term is set to end.

Breyer's warning and slight reference to abortion precedent

Breyer spoke up in a dissent in a case concerning whether the Constitution permits a state to be sued by a private party in the court of another state, without consent. Breaking along ideological lines, the conservative majority held that the state is immune from such a lawsuit and overruled some 40-year-old precedent.

At the end of a long dissent, Breyer, writing for his liberal colleagues, took on the issue of justices overturning precedent.

"Overruling a case always requires special justification," Breyer wrote. "What could that justification be in this case?"

"I understand that, because opportunities to correct old errors are rare, judges may be tempted to seize every opportunity to overrule cases they believe to have been wrongly decided," Breyer wrote. "But the law can retain the necessary stability only if this court resists that temptation, overruling prior precedent only when the circumstances demand it."

Breyer was clearing echoing the sentiments of Justice Elena Kagan, writing for her liberal colleagues, last term when she criticized the conservatives for overturning 1977 precedent in a 5-4 case that dealt a major blow to public sector unions.

What turned heads was that in making his argument, Breyer also cited Planned Parenthood v. Casey, a landmark abortion opinion from 1992 that affirmed key provisions of the 1973 case Roe. v. Wade. Breyer is well aware that the court has several petitions before it asking it, not to overrule Roe directly but to chip away at abortion rights.

Was Breyer putting his colleagues on notice of future battles as they consider their next moves over this term and next?

"Today's decision can only cause one to wonder which cases the court will overrule next," Breyer wrote.

Death penalty feud

Also on Monday, the justices shed more light on their deep divide over the application of the death penalty. The disagreement is not only pitting liberals against conservatives, but the far right of the court against Chief Justice John Roberts and Kavanaugh in one particular dispute.

While the Supreme Court prides itself by "showing its work" in pages and pages of opinions issued each year, the justices rarely offer a glimpse of the fraught atmosphere that leads up to last minute death penalty appeals.

Since late last year, however, the justices' disputes have spilled out in public. Monday was no different, when seemingly out of the blue, Justice Samuel Alito, Neil Gorsuch and Clarence Thomas bickered openly about an execution the court's majority put on hold back in March. The case concerned a Buddhist, Patrick Murphy, who sought to have his spiritual adviser present with him in the execution chamber in Texas. At the time, only Thomas and Gorsuch publicly dissented from the stay of execution.

But on Monday, Alito said that he wanted to explain for the first time why he too thought the court's majority had gotten it wrong.

First, Alito reiterated the facts of the crime that occurred on Christmas Eve in 2000 when police officer Aubrey Hawkins was shot "11 times" and "dragged from his vehicle." Throughout the years, Murphy unsuccessfully pursued post-conviction relief to no avail. Alito pointed out that it was only "about three months after Murphy's execution date was set that his attorneys asked that his spiritual adviser be present."

Alito accused the majority of the court of "countenancing" delay tactics brought by Murphy and concluded by saying that the "court invites abuse."

Although no liberals responded on Monday, Kavanaugh and Roberts decided to do so. The two justices said that the prison's policy was discriminatory because it allowed Christian and Muslim advisers, but not Buddhists. The policy has since been changed.

Kavanaugh wrote that he "fully" agreed with Alito that lawyers often attempt to delay death sentences, but that Murphy's case was "highly unusual."

The "statement" from Kavanaugh, joined by the chief justice, suggested the two justices did not want Alito's opinion to be the last word without a response, and they wanted to stress that they agree that last minute appeals are problematic.

"Put simply, this court's stay facilitated the prompt resolution of a significant religious equality problem with the State's execution protocol and should alleviate any future litigation delays or disruptions that otherwise might have occurred as a result of the State's prior discriminatory policy," Kavanaugh wrote.

Kavanaugh sides with the liberals in Apple case

Kavanaugh sent a jolt through the business community by casting the deciding vote with the liberals in a 5-4 case against Apple.

In an opinion penned by Kavanaugh, the court held a group of iPhone owners could bring a lawsuit accusing Apple of violating US antitrust rules.

He stressed that the case was at an "early pleadings stage of litigation" and that the court wasn't assessing the merits of the antitrust claim, but that he thought the claims should be able to proceed.

"The plaintiffs seek to hold retailers to account if the retailers engage in unlawful anti-competitive conduct that harms consumers who purchase from those retailers," Kavanaugh wrote.

"That is why we have antitrust law," he said.

"The case challenged the fact that Apple charges a high commission to app developers, which indirectly harms consumers, the Supreme Court held that because consumers interface directly with Apple they could sue," said Colin Kass a lawyer at Proskauer. "It's unusual that Kavanaugh would side with a liberal minority particularly because the dissent is significantly more business-friendly."