The U.S. Supreme Court on Thursday cleared the way for a civil rights lawsuit against a Houston-area traffic officer who shot and killed a fleeing man, ruling that courts must weigh the full sequence of events — not just the instant a threat arises — when deciding if police used excessive force.

The decision broadens legal protections for civilians and could open new avenues for holding officers accountable for split-second decisions they make during encounters, especially when it was their own actions that put them in danger.

In a unanimous ruling, the Supreme Court concluded that lower courts erred in dismissing a civil suit against Roberto Felix Jr., who fatally shot 24-year-old Ashtian Barnes during a 2016 traffic stop in Houston. The court found the Fifth Circuit erred in upholding that decision.

The majority opinion by Justice Elena Kagan held that the Fourth Amendment requires courts to consider the "totality of circumstances," including whether an officer's actions prior to a shooting helped create the danger they later claim justified deadly force.

Writing for the majority, Justice Kagan said that "by limiting their view to the two seconds before the shooting, the lower courts could not take into account anything preceding that final moment."

The decision reinforces precedent the Supreme Court set in 1989 with the case Graham v. Connor, where the court first embraced the "totality of circumstances" approach. Eight circuit courts have been using such a test when probing excessive force claims, while the Second, Fourth, Fifth and Eighth circuits have only looked at the "moment of threat" arising in a police encounter.

"While the situation at the precise time of the shooting will often matter most, earlier facts and circumstances may bear on how a reasonable officer would have understood and responded to later ones," Justice Kagan wrote.

The ruling sends the case back to the lower courts where Barnes' estate will get a renewed chance to argue that Felix provoked the fatal confrontation.

The shooting occurred on April 28, 2016, after Felix, a traffic enforcement officer with the Harris County Precinct 5 Constable's Office, pulled Barnes over on a Houston highway, citing unpaid tolls linked to the rental car Barnes was driving. Barnes, who was unarmed, ignored instructions to get out of the car and instead began to slowly drive away.

Felix leapt onto the hood of the moving car and, seconds later, shot Barnes through the windshield. The officer later claimed he fired in self-defense, believing Barnes' erratic driving put his life at risk.

Barnes' mother, Janice Hughes Barnes, sued Felix and Harris County in Texas state court under Section 1983 of the federal civil rights statute, alleging excessive force in violation of the Fourth Amendment. Felix invoked qualified immunity, a legal doctrine that shields officers from civil liability unless they violate clearly established constitutional rights.

The case was moved to federal court, where U.S. District Judge Alfred H. Bennett sided with Felix. The court found the shooting was reasonable under the Fifth Circuit's moment-of-threat doctrine, which limits judicial review to the seconds before force is used.

Still, Judge Bennett noted in his decision that the doctrine was too narrow and that by following it the Fifth Circuit "has effectively stifled a more robust examination of the Fourth Amendment's protections when it comes to encounters between the public and the police." The judge ultimately said he was bound to apply the rule.

On appeal, the Fifth Circuit upheld the district court's ruling, calling the moment-of-threat framework "well established" and refusing to consider whether Felix's decision to jump onto the moving car had contributed to the deadly outcome.

"We may only ask whether Officer Felix was in danger at the moment of the threat," the panel wrote. "Any of the officer's actions leading up to the shooting are not relevant."

In a separate concurrence, U.S. Circuit Judge Patrick Errol Higginbotham warned that the doctrine conflicted with Graham v. Connor, and called on the justices to resolve the circuit split.

Attorneys for Barnes' mother saw a path opening. They appealed to the Supreme Court in May, arguing the doctrine was "profoundly wrong" and that Felix had no legitimate reason to kill an unarmed man who posed no imminent threat.

During oral arguments on Jan. 22, several justices signaled unease with adopting a legal standard that narrowly looks at the exact moment a threat arises during a police encounter.

Charles L. McCloud of Williams & Connolly LLP, who argued on behalf of Felix, told the justices that once an officer is in danger, the use of deadly force is presumptively reasonable.

"That conclusion should end this case," he said.

Justice Kagan suggested sending the case back to the lower courts to assess the broader circumstances.

"It seems as though we should kick it back and let you guys fight it out," she told the attorneys.

Justice Brett Kavanaugh appeared less sympathetic toward Barnes' arguments.

"What's an officer supposed to do when at a traffic stop and someone pulls away, just let them go?" he asked.

Arguing for Barnes, Nathaniel Avi Gideon Zelinsky of Hogan Lovells responded by saying that Felix could have opted to chase Barnes in his car or request backup from other police units instead of shooting.

Janice Hughes Barnes and the Estate of Ashtian Barnes are represented by Nathaniel Avi Gideon Zelinsky of Hogan Lovells.

Roberto Felix Jr. and Harris County are represented by Charles Luther McCloud of Williams & Connolly LLP.

The case is Janice Hughes Barnes, Individually and as Representative of the Estate of Ashtian Barnes v. Roberto Felix Jr. et al., case number 23-1239, in the Supreme Court of the United States.

--Editing by Brian Baresch and Alex Hubbard.

Update: This story has been updated with further information.