U.S. Supreme Court justices on Wednesday seemed reluctant to raise the standard police must meet to enter a home without a warrant during a potential emergency, with several saying they did not see a reason to disturb past rulings on the subject.

The key question is how much evidence of danger law enforcement must have to support entering a home under an emergency-aid exception.

The petitioner, a Montana man shot by police in his home, contends officers should have to establish probable cause. This would be a higher bar than the "objectively reasonable basis" standard that the court previously set out in its Brigham City v. Stuart opinion in 2006 and Fischer v. United States in 2009

Justice Elena Kagan told the petitioner that she believed it was a bad idea to apply probable cause — a term that applies to the level of proof that a crime has occurred — in a non-criminal context.

"I guess what I'm saying is maybe in those two cases, we did, like, the best thing possible, and we're not going to be able to do anything better," she said.

In this case, petitioner William Trevor Case seeks to reverse a Montana Supreme Court decision that Anaconda-Deer Lodge County police officers lawfully entered his home in 2021 after Case's ex-girlfriend reported he told her he was going to shoot himself.

Once inside his home, responding officers shot Case, who was allegedly hiding in a closet with a gun. Case was later charged with assault on a peace officer.

Montana's high court ruled that the officers did not violate Case's Fourth Amendment rights when they entered his home because they had an objectively reasonable basis to believe he was in danger. The officers did not need a warrant to enter, nor did they need probable cause, because the situation was "totally divorced" from a criminal investigation, the Montana Supreme Court said.

On Wednesday, Case's attorney, Fred Rowley Jr. of Wilson Sonsini Goodrich & Rosati, argued that an "objectively reasonable basis" is too low of a bar for a key Fourth Amendment right.

"There is no liberty interest more deeply rooted in the Fourth Amendment than the sanctity of the home," Rowley told justices. "The Court has long recognized that physical entry of the home is the chief evil against which the wording of the Fourth Amendment is directed."

But the facts of this particular case gave justices pause.

Officers knew Case as someone who had a history of alcohol abuse and mental health issues. Officers also were aware that Case had made suicidal threats at the school where he taught, leading to a lockdown because he had a weapon. In another encounter with police, Case allegedly tried to provoke officers into shooting him in what officers saw as an attempted "suicide-by-cop," according to court documents.

After receiving a call from his ex-girlfriend, officers checked the windows of his home and saw an empty handgun holster on a table, empty beer cans and a notepad on a table.

"It seems to me that if the police could not enter this house based on the facts that they knew, then I don't know when the police are ever going to be able to enter a house to prevent somebody from committing suicide," Justice Samuel Alito said.

Justice Neil Gorsuch said current case law says that private citizens have a defense against trespassing when it reasonably appears necessary to prevent serious harm to the occupant, and that applies also to police.

"Now, that doesn't give them a license to go rummage about the place for crimes, but it does give them a license to enter to render assistance, I would have thought," Justice Gorsuch said.

Montana Solicitor General Christian Corrigan argued that the Brigham standard is "more flexible" than probable cause, and that probable cause is specifically linked to criminality rather than belief that there is an emergency.

He said probable cause is a "single determination" that a certain threshold of evidence has been reached. "But objective reasonableness, as in this case, can be a progressive analysis," Corrigan said.

Zoe Jacoby of the U.S. Solicitor General's Office urged the justices to adhere to the Brigham standard of objective reasonableness.

"The framers adopted the Fourth Amendment to guard against overzealous criminal investigation, not to hamstring officers from providing life-saving aid to people in need," she said. "Yet, petitioner's rule would make it harder for government officials to help people in crisis, from victims of domestic violence to older people who have fallen and can't get up."

Fred A. Rowley Jr. of Wilson Sonsini Goodrich & Rosati PC argued for Case.

Montana Solicitor General Christian B. Corrigan argued for the state.

Zoe A. Jacoby of the U.S. Solicitor General's Office argued for the federal government in support of Montana.

The case is William Trevor Case v. Montana, case number 24-624, in the Supreme Court of the United States.

--Additional reporting by Marco Poggio and Katie Buehler. Editing by Emily Kokoll.