When District of Columbia police officers Andre Parker and Anthony Campanale responded to reports of unauthorized goings-on at a supposedly vacant home nearly a decade ago, they probably didn’t expect the evening’s events to lead to all the way to the U.S. Supreme Court. But that’s exactly what happened in District of Columbia v. Wesby, in which the justices are scheduled to consider whether the arrests that the officers made that night violated the Fourth Amendment, along with whether – even if they did – the partygoers can sue the arresting officers, or the police are instead immune from suit.

In March 2008, Parker and Campanale arrived to investigate neighbors’ reports of a party and “illegal activities” at an unoccupied house. When the two approached the house, many of the 21 people inside ran upstairs or moved into different rooms. The officers found that there had indeed been a party (of sorts) in progress: Among other things, they found women who had apparently been selling “lap dances” and were “dressed only in their bra and thong with money hanging out [of] their garter belts”; the officers also smelled marijuana. Some of the partygoers told the officers that they had been invited to the house, while others told the officers that they had received permission to be there from a woman whose name was either “Peaches” or “Tasty.” But “Peaches” gave the officers conflicting stories about whether she had permission from the owner to use the house. When police officers eventually talked to the owner, he confirmed that he had not authorized anyone, including “Peaches,” to be at his house.

The officers arrested the partygoers for trespassing and took them to the police station, where a commander opted to charge them with disorderly conduct instead. Those charges were eventually dropped, but 16 partygoers went to federal court, arguing that the police had lacked probable cause to arrest them. The district court agreed, ruling that police had not learned anything in the house to suggest that the partygoers “knew or should have known that they were entering against the owner’s will.” After a trial, the court ordered the officers to pay nearly $700,000, plus attorneys’ fees.

The U.S. Court of Appeals for the District of Columbia Circuit affirmed, concluding that the officers lacked probable cause to arrest the partygoers because they had no reason to believe that the partygoers either knew or should have known that they were not allowed in the house. In the court’s view, the homeowner’s statement to the police that he had not given anyone permission to enter the house was not enough, because the homeowner “never said that he or anyone else had told” the partygoers that they were not welcome. Indeed, the court reasoned, there was “no evidence that the officers had asked either Peaches or” the homeowner whether the partygoers “knew that Peaches had no right to be in the house.” After the full court of appeals denied rehearing, over the dissent of four judges, the District of Columbia government and the officers asked the Supreme Court to weigh in, which it agreed to do last winter.

The District of Columbia and the police officers argue that whether there was probable cause to arrest the partygoers turns on whether, in light of all the facts, the officers could have reasonably believed that the partygoers were trespassing. That test is easily met here, they contend, even if the partygoers told police that they believed they were authorized to be in the house: They were in the vacant house late at night; officers smelled marijuana and saw women who were barely clothed; the partygoers scattered (and one was found hiding in a closet) after police entered the house; the homeowner had told police that they didn’t have permission to be there; and even “Peaches” had admitted that she didn’t have authorization from the homeowner. Police officers should not be required to determine exactly what a suspect knows before arresting him, particularly when virtually all suspects will profess innocence. If it is allowed to stand, the government and the officers conclude, the D.C. Circuit’s decision will “have a broad chilling effect on law enforcement officers when making on-the-scene credibility judgments, adversely affecting their everyday ability to do their jobs and protect the public.”

Even if the Supreme Court rejects the police officers’ argument that they had probable cause to arrest the partygoers, the officers could still prevail on another ground: Their claim that they generally cannot be sued, known as qualified immunity. The Supreme Court’s cases impose a high bar on lawsuits for damages against public officials, shutting down suits like these against police officers as long as the officers’ conduct does not run afoul of “clearly established law.” But there is no such clearly established law here, the officers tell the justices; if anything, the decisions by the District of Columbia’s highest court “have found probable cause to arrest under similar facts.” And at the very least, that court’s earlier cases certainly did not establish “beyond doubt” that there was no probable cause to arrest the partygoers – as evidenced by the fact that four judges on the federal court of appeals agreed that the officers did have probable cause.

The partygoers depict their case as an easy one. In their view, it was clearly established that the officers had probable cause to arrest them for trespassing only if there was evidence supporting each element of the crime – including, in this case, the requirement that the partygoers knew or should have known that they were not supposed to be in the house. But here, they suggest, their only offense was being “invited guests at a standard, though debauched, house party in a cheaply furnished house in a poor neighborhood.” Police officers had no reason to believe that the partygoers “interrogated (or should have interrogated) their host about” whether she was actually renting the house from the homeowner or otherwise had permission to be there. Therefore, not only did the police officers lack probable cause to arrest them, but the lack of probable cause was so clearly established that the officers are not entitled to qualified immunity.

The partygoers may see the case as straightforward, but it’s not clear that the Supreme Court (at least so far) agrees. The justices considered the case at nine consecutive conferences before finally granting review. That kind of extended consideration often signals either that the court is preparing to summarily reverse (that is, reverse without briefing on the merits or oral argument) the lower court’s ruling or that a justice is dissenting from the denial of review. We likely will never know what was going on behind the scenes, but we will learn a lot more about the justices’ current views after the oral argument.

This post was also republished at SCOTUSblog.com.