Earlier this month, the U.S. Supreme Court ruled that government officials, except in cases of clear incompetence or intentional law breaking, can use deadly force against unarmed civilians.

The ruling was for a case, Kisela v. Hughes, which involved officer Andrew Kisela of the University of Arizona Police Department. In 2010 he, along with three other officers, responded to a 911 report of a woman, Amy Hughes, behaving erratically with a large kitchen knife. Ultimately, Hughes was shot four times by Kisela, but survived the encounter.

The facts of this shooting, one of hundreds that occur every year throughout the country, made its way to the Supreme Court after Hughes sued the UAPD. She alleged that the officer violated her Fourth Amendment right from unlawful seizure because of his excessive use of force. But in a per curiam decision, in which the court ruled as a singular body rather than through individual opinions, ultimately ruled that the officer’s use of force was justified. Two justices, Sonia Sotomayor and Ruth Bader Ginsburg, dissented to the ruling.

“The rationale the court has typically used is one that’s more deferential to local law enforcement,” said Jesus Alonso, a law student at the University of Arizona who is studying police use of deadly force. “Since the 1980s, the prevailing view is through the lens of what the police officer, in the heat of the moment, views as a reasonable response to a dangerous situation.”

The vast majority of civilian’s fatal encounters with police never end in suspension, punishment or arrests. Some believe this is because of their authority to respond to perceived threats without fear of liability, even when their use of force might not be justified. According to data from the Cato Institute’s National Police Misconduct Reporting Project, only about a third of criminal cases brought against police in the U.S. result in convictions, and a third of those convictions result in prison sentences.

But proponents of police having greater latitude to use force say that these low conviction and arrest rates may just reflect effective training and lawful conduct. Officers at all levels of law enforcement, whether federal, state or university, must be trained to use a wide range of de-escalation and force techniques to handle potentially violent suspects.

“We require officers to go through annual use of force training,” said Deputy James Allerton of the Pima County Sheriff’s Department. “We look at the techniques they’re trained in as a continuum: verbal communications, soft empty hand control, tasers, impact weapons like batons, and deadly force.”

Kisela, before opening fire, verbally commanded the woman multiple times to drop her knife. As Hughes continued to clutch the weapon, her roommate, who made the 911 call, started to approach her in an attempt to de-escalate the situation herself. As she got within six feet of Hughes and the knife, Kisela determined that deadly force was necessary to prevent any potential loss of life and fired his weapon.

“Officers aren’t necessarily taught to use deadly force as a last resort,” said Allerton. “They’re taught to employ it when they reasonably believe either their life or the life of another individual is immediately at stake.”

But many people fear that expanding situations in which a police can take life without fear of liability, under a doctrine called qualified immunity, can negatively impact the public’s trust of law enforcement.

“I agree with Justice Sotomayor, in that this ruling can send the wrong message to civilians and law enforcement,” said Stephen Portell, a Tucson attorney who specializes in civil litigation and has practiced for the last 21 years.

“The more you expand qualified immunity through the courts, the more we lose the ability as civilians to make inquiries about whether the use of force was justified,” said Portell. The courts, which grant officers qualified immunity if they were found to have acted reasonably and not broken any laws, are greatly influenced by precedents set by the Supreme Court, like the Kisela decision.

According to Sotomayor’s dissent, the Fourth Amendment serves as a sort of deterrent against reckless or harmful conduct. The more that deterrent is chipped away through exceptions found by the court, the more likely police are, in her words, to “shoot first and think later.”

But Portell doesn’t believe that a significant amount of officers are reckless or trigger-happy. He points out that in addition to annual retraining on using guns, police departments have commissions called ‘shooting boards’ that evaluate the reasonableness of an officer discharging his or her firearm while on the job.

“The majority of men and women who become police officers do so out of profound respect for the U.S. Constitution,” he said. “That’s why I think even police officers wouldn’t be pleased with this ruling, because it carves a bigger hole in Fourth Amendment protections for people.”

Portell, like many other opponents of the court’s ruling, believes that jurors should play a greater role in defining the contours of an officer’s justification in using deadly force through a case-by-case basis.

“If we remove the public’s role in this, then public confidence in our law enforcement could suffer,” he said.

But determining how to hold an officer accountable is a vexing task, especially when considering the split-second decisions that many officers need to make in high-intensity, usually violent situations.

“The court usually tries to shy away from getting to involved in more local matters, like an officer using deadly force,” said Alonso. “Even proponents of holding more officers accountable have trouble defining specific standards of how to do so.”

Until then, the doctrine of qualified immunity will continue to play a greater role in protecting police from public inquiries into their use of fatal force. As of now, data on the rates of police shootings, whether justified or not, is sparse and not very detailed. A recent comprehensive study, done in 2015 by RTI International, couldn’t get information on nearly 28% of law enforcement homicides between 2003 and 2009.

Until more data is uncovered, it will be difficult for the public to accurately gauge how pervasive unjustified killings are in the U.S.