Boston police are having trouble finding volunteers to wear body cameras for a pilot program, leading Commissioner William B. Evans to say Thursday night that the department is probably going to have to force officers to wear the devices.

Evans, at a hearing of the City Council Committee on Public Safety and Criminal Justice, said police hope to launch the six-month program, which will outfit up to 100 officers with body cameras in five districts across the city, on Sept. 1.

“It’s looking like we’re probably not going to have volunteers,’’ Evans said. “And officers most likely are going to be assigned’’ to wear them.

Last month, police officials reached an agreement with the department’s largest union to outfit the officers with cameras on a voluntary basis. But Evans said Thursday that finding volunteers has been “a hard sell,’’ in part because the union initially resisted the idea.

He said no volunteers had come forward by the beginning of the week, and he was unsure how many had stepped up as of Thursday night, if any. All participants will receive a $500 stipend over the life of the initiative, as part of the city’s deal with the patrolmen’s union.

The issue of volunteers has been a major sticking point for the pilot, with civil rights advocates contending that only officers with clean disciplinary records would agree to wear the cameras, skewing the results of the trial.

The Boston Police Patrolmen’s Association could not immediately be reached for comment on Thursday night.

Before Evans spoke at the meeting at a Mattapan community center, civil rights advocates reiterated several concerns they have raised.

Among the key points of contention is a provision that allows officers to review video footage from the cameras before filing reports on an incident.

“This is a major concern of citizens across Boston,’’ said Shekia Scott of the Boston Police Camera Action Team, a group pushing for the cameras.

Scott and other advocates said allowing officers to view footage before filing reports could improperly influence their official statements about an encounter.

But Evans defended the provision, stating that law enforcement researchers, including a top adviser to President Obama, have concluded that permitting officers to see the footage is “the right thing’’ to do.

He said an officer may initially have trouble recalling what occurred during a heated encounter, and video could ensure accuracy. “What harm is [there] in getting the most accurate picture?’’ Evans said.

City Councilor Tito Jackson disputed that notion, noting that filing a false report is “an offense.’’

According to the department policy for the pilot, officers or supervisors involved in, or witness to, a shooting will not be allowed to view a recording before investigators. But the officers will be allowed to view recordings made by their cameras before providing a statement to investigators.

Other criticisms voiced Thursday targeted provisions that allow officers to turn off cameras in certain situations, as well as language stating that police will not be disciplined for minor violations of camera operating procedures.

Nia Evans of the Boston NAACP said police in other cities “have been caught selectively recording several times’’ when it is not permissible.

She said providing officers overly broad discretion for shutting off cameras “can undermine’’ the program’s integrity.

The Boston policy states that officers may disable cameras at their discretion when recording could be considered insensitive or inappropriate, or when it is prohibited by privacy policies, among other factors.

Regarding penalties for violations, Evans said Thursday that “if clearly [an officer] is tampering with [footage] this will be dealt with severely.’’

The rollout of the program comes amid a nationwide debate over police use of force following killings of black suspects by officers in other states and retaliatory killings of police. City officials will analyze the data along with outside researchers before deciding whether to implement body cameras department-wide.

But Evans suggested Thursday that the city is heading in that direction, telling the crowd of about 70 people that authorities have committed to the notion that “if the public wants it, then we’re going for it.’’

Jan Ransom of the Globe staff contributed to this report. Travis Andersen can be reached at travis.andersen@globe.com.