Among the first demands from outraged demonstrators as they gathered Tuesday afternoon outside the convenience store where Alton Sterling was shot by a Baton Rouge police officer was for an outside agency to take over the criminal probe into the fatal police shooting.

By the next morning, the U.S. Department of Justice and the FBI announced they’d agreed to do just that, and Baton Rouge police detectives turned over their files to federal agents.

Whether this heralds a more widespread change in how police shootings are investigated in Baton Rouge remains up the air. While the federal probe into the Sterling shooting is ongoing, Louisiana State Police have an agreement with the Baton Rouge Police Department that troopers will automatically handle any officer shooting that involves city police, said Col. Mike Edmonson, the State Police superintendent.

But there is no agreement at this time for the state agency to take over shooting investigations involving Baton Rouge officers on a permanent basis, although Edmonson said he’s had discussions with local officials.

East Baton Rouge Parish Sheriff Sid Gautreaux struck such an arrangement with State Police earlier this year, not long after calling on State Police detectives to investigate the Feb. 23 shooting death of Travis Stevenson, an otherwise unarmed 48-year-old Baton Rouge man who allegedly attempted to ram deputies with his car.

Activists and black community leaders have urged the Police Department to change protocols and turn to an outside agency — likely the State Police — to promote community trust and transparency. Experts in policing say bringing in investigators from outside the agency after fatal shootings provides for greater objectivity, reducing concerns about the camaraderie and personal relationships between officers in a department that many fear can taint an investigation.

Distrust of internal probes

Under the Baton Rouge Police Department’s usual procedure, officers from the department’s internal affairs division and homicide detectives would launch simultaneous — and strictly separate — investigations into a police shooting or other killing, said Cpl. L’Jean McKneely, a spokesman for the department.

An internal affairs review of the Sterling slaying, which is tasked with determining whether officers broke the Police Department’s use-of-force and other policies during the altercation and shooting, continues even after federal authorities took control of the criminal investigation.

The Sterling shooting has captured national attention, the first of two shootings of black men by police officers caught on video last week. When the cellphone video ­— showing two officers on top of Sterling, pinning him to the ground, and then one officer shooting him — was released late Tuesday, it quickly sparked outrage in Baton Rouge, which only increased when another video taken from a different angle circulated the following day.

Critics noted that Sterling did not have a weapon in his hand, although police have said he was armed and an officer in one video can be seen removing an object from his pocket after he was shot. Officers Blane Salamoni and Howie Lake II responded to the scene outside the Triple S store on North Foster Drive early Tuesday morning in response to a call that a man selling CDs outside the store pointed a weapon at somebody.

A source familiar with the investigation has identified Salamoni as the officer who shot 37-year-old Sterling.

Local NAACP President Mike McClanahan, who was among those demanding an independent review of the Sterling shooting Tuesday, said large portions of the black community in Baton Rouge lack faith in police shooting investigations, pointing to the country’s long history of racial injustice.

“You can’t tell me I need to trust the process when the process has been tainted for hundreds of years,” said McClanahan. “It’s always been a process we do not trust.”

Although many small, mostly rural Louisiana departments have long relied on larger agencies — such as the State Police — to investigate officer shootings, handling these probes internally is “the rule in most police departments in the United States,” said Merrick Bobb, a national expert in police accountability and director of the Police Assessment Resource Center in Los Angeles.

Bobb said he couldn’t comment directly on the Baton Rouge Police Department, because he hadn’t studied its past investigations, but said he didn’t believe investigations by outside agencies are necessary in every case.

“I think there are cities and systems where there are internal investigators and law enforcement people that are good and stand up when measured against best practices,” Bobb said. “I don’t think there’s a one rule fits all.”

But with the perception of police departments in many communities badly tarnished, especially amid growing scrutiny of officer use of force over the past two years, an outside investigation of controversial police shootings is now a necessary step to building trust in an investigation’s conclusions, said Dennis Jay Kenney, a professor of criminal justice at John Jay College in New York City and a former Florida police officer.

“At this point, an external investigation with these sorts of incidents is almost mandatory,” said Kenney. “The police brand is now pretty badly damaged. Very much the concern is now that the benefit of the doubt no longer rests with them.”

Kenney described the pressure in high-profile police shootings as “withering,” especially for detectives at a department reviewing an incident involving their own colleagues. Public demands from protesters and politicians for an arrest can weigh on investigators, Kenney said, alongside an often stronger pull “to side with the officer ... and to avoid bringing charges if at all possible.”

State Rep. Ted James, a Democrat who represents north Baton Rouge and has been at many of the protests since Sterling’s death, said he’s considering possible legislation to require the investigations of fatal officer shootings in Louisiana to be turned over to the State Police or another independent agency.

“I honestly think it’s beneficial for both sides. It’s not an indictment of our own agencies,” James said. “You don’t want any accusations or the appearance of foul play.”

New DA protocol

Hillar C. Moore III, the East Baton Rouge Parish district attorney, recently overhauled his office’s handling of fatal police shootings after spending several years examining procedures in prosecutors’ offices elsewhere.

Under the new protocol, put into practice for the first time during the investigation of the Baton Rouge Police Department’s killing of 22-year-old Calvin Smith in February, assistant district attorneys are directly involved in investigations, examining evidence and observing interviews with the officers and potential witnesses. Those procedures were in place during the initial investigation of Sterling’s death before the FBI stepped in.

Moore also promised far greater transparency around his decisions on whether to charge officers with criminal offenses. In cases where Moore’s office clears police of criminal wrongdoing — such as in the killing of Smith, which Moore called “not only warranted but necessary to protect (the officers) and the public” — the district attorney has pledged to issue a public report laying out the evidence in the case and his reasons for refusing to prosecute.

Moore said the work done by State Police detectives — drawn from barracks outside of the capital city — on two shootings involving East Baton Rouge Parish sheriff’s deputies has been “outstanding.”

“I anticipate that the Baton Rouge police will eventually adopt the same model and we’ll have completely independent officer-involved shooting investigations for the entire parish,” Moore said. “I think that’s the model to go to.”

Some experts and activists, though, also have questioned whether local district attorneys like Moore — who work closely with local law enforcement and rely heavily on the credibility of police officers in other cases — can objectively handle cases of police shootings.

Moore has defended his ability to prosecute such cases, saying he’s ultimately accountable to the people during elections, but he added that it’s still “premature” to say whether he’d recuse himself from the Sterling case. While federal investigators and prosecutors are investigating the case and could choose to bring federal civil rights charges — if they conclude charges are warranted at all — the possibility also remains for the case to be handed back to the local prosecutor for consideration of state charges.

Moore also said proposals to have district attorneys from neighboring jurisdictions handle police shootings is “something for folks to consider.”

The rapid public reaction and extensive media coverage of fatal police shootings present another major challenge to gaining community trust in investigations, independent or otherwise, Kenney said. Many in the public will have made up their minds about a case long before an investigation — which could last several weeks or even months — comes to a conclusion.

“The sense is very much that police never get indicted and, even when they do, they never get convicted. As long as that’s perceived, you’re going to have tremendous problems in the community, understandably,” he said. “The need is to demonstrate that you apply the rules as fairly to yourself as you do to the community.”

Advocate reporter Maya Lau contributed to this story. Follow Bryn Stole on Twitter, @BrynStole .