When the Georgia authorities attempted to clear protesters from forested property near Atlanta in January, to make way for the construction of a $90 million police and fire training facility, a confrontation with a group of activists who deride the project as “Cop City” led to a barrage of gunfire.

One state trooper was wounded, and officers killed a 26-year-old environmental activist named Manuel Esteban Paez Terán. Months later, the shooting remains under investigation, with the activist’s friends and relatives disputing the official account that Terán fired first, wounding the trooper.

Investigators, who recently turned evidence about the episode over to a special prosecutor, say the trooper and other members of a law enforcement task force who were near the shooting were not wearing body cameras. The lack of direct video evidence has intensified questions about what happened, and prompted calls for more police agencies to consistently record their actions.

“Why they didn’t use cameras, I don’t know,” said the activist’s mother, Belkis Terán, who has called for an investigation of her child’s death to be conducted independently of the Georgia authorities. “I don’t trust them,” she said.

Relatively rare a decade ago, police-worn body cameras have been more widely adopted in the wake of the fatal 2014 police shooting of Michael Brown, 18, in Ferguson, Mo. In some cases, police forces began using them as a result of federal civil rights investigations. Over the last decade, they have become an important tool both for police investigations and for efforts to hold law enforcement agencies accountable for misconduct.

“You’re introducing a level of evidence that is able to produce a better outcome,” said Volkan Topalli, a criminology professor at Georgia State University. Professor Topalli has contributed to a body of research indicating that, compared with police departments that do not use the cameras, those that do face fewer public complaints, and their investigators clear more cases.

A dramatic example of the cameras’ impact occurred less than two weeks before the shooting outside Atlanta in January, when body cameras and other surveillance video captured images of police officers in Memphis beating Tyre Nichols, 29, who later died from his injuries. The footage led to several firings, and five officers were charged with murder.

The rapid adoption of body cameras, especially by departments in many of America’s largest cities, has led to a greater expectation by the public that law enforcement actions will be caught on camera — and greater suspicion when they are not. Several city police chiefs recently pushed the Justice Department to allow the release of footage from cameras worn by local officers serving on federal task forces, saying the step was needed to fulfill public expectations of transparency.

Still, the use of body cameras continues to vary widely, and only seven states have enacted requirements for them, according to the National Conference of State Legislatures.

In Georgia, the police chiefs association reported that nearly 90 percent of the 254 local agencies it surveyed in 2021 were using body cameras in some fashion. But the Georgia State Patrol, with nearly 800 troopers, does not routinely equip its officers with them, relying instead on dashboard cameras. Nor does the Georgia Bureau of Investigation, which was part of the forest-clearing task force and led the investigation of Terán’s death.

Because most troopers operate primarily from their vehicles, only three Georgia State Patrol units — those at the State Capitol and the tourist destination of Jekyll Island, and a motorcycle unit in metropolitan Atlanta — currently use body cameras, according to Courtney Floyd, a spokeswoman for the agency. “Every marked patrol car has a permanently mounted, in-car dash camera,” she said.

Some other state police forces share that policy, said John Bagnardi, executive director of the American Association of State Troopers. Although his organization does not track body camera use, he said, “I know some states prefer the dash cameras, as much of their work is performed in and around the vehicle.”

In the wake of the Terán shooting, Democratic legislators in Georgia proposed requiring body cameras for all law enforcement officers in the state, but the bill failed to reach the floor for a vote. State Representative Sandra Scott, one of the bill’s sponsors, said opposition to the bill stemmed from a desire to shield police forces from accountability. “We still have officers that are doing things they should not be doing,” she said.

But the Georgia Sheriffs’ Association, which helped block the proposal, said it was opposed to requiring agencies to use body cameras without providing money for them. The cameras can cost about $1,000 apiece to buy, plus expenses for maintenance and video storage, and cost is a common concern cited by agencies that have not yet adopted them.

Some critics of the police say that body cameras have done little to curb misconduct. “Police are willing to kill on camera,” said Micah Herskind, a policy associate at the Southern Center for Human Rights, citing the recent deaths of Mr. Nichols in Memphis, George Floyd in Minneapolis and Rayshard Brooks in Atlanta, all of which were recorded.

Even experts who support the use of body cameras caution that the footage can sometimes be misleading or subject to varying interpretations. “People disagree about policing, and will continue to disagree about exactly what a video shows,” Seth W. Stoughton, a University of South Carolina law professor and former police officer, told The New York Times for a 2016 video investigation.

The January incident outside Atlanta occurred in the South River Forest in DeKalb County, where the city plans to build an 85-acre training center on land it owns. The project has prompted months of intense protests from activists who want to preserve the nearly 400-acre forest, and who oppose what they call the further militarization of policing.

Investigators have said that officers from the forest-clearing task force tried to order Terán out of a tent in the forest, and then the activist shot a state trooper, prompting other officers to return fire. The Georgia Bureau of Investigation has said that gunshot residue was found on the activist’s hands, and records indicate that Terán had purchased the firearm used to shoot the trooper.

But members of the activist’s family maintain that Terán, who was nonbinary and was known among the forest activists as Tortuguita, or Little Turtle, was a pacifist. The family commissioned its own autopsy, which found that Terán was shot while sitting cross-legged, with hands raised. The family’s autopsy found no trace of gunshot residue, and neither did an official autopsy conducted by the medical examiner in DeKalb County, which indicated that Terán sustained at least 57 gunshot wounds.

Though investigators say no video images of the shooting were captured on camera, audio was. Footage released by the Atlanta Police Department, whose officers wear body cameras and were in a different part of the forest, includes the sounds of distant gunfire and the voices of officers discussing friendly fire. Activists have seized on the exchange, suggesting that troopers had wounded one of their own.

In a statement after the footage was released, the state bureau acknowledged that “at least one statement exists where an officer speculates that the trooper was shot by another officer in crossfire.” But it added: “Speculation is not evidence. Our investigation does not support that statement.”

The bureau turned the case over last month to a special prosecutor, George Christian, who is the district attorney for the Mountain Judicial Circuit in northeast Georgia. In a statement this week, Mr. Christian said he was working to determine “whether or not the use of lethal force was authorized,” and had not finished reviewing the evidence. He did not say when he would reach a decision.