Ask Curtis Rollins how many times he’s been stopped and searched by police, and you get a slightly more nuanced version of the “too many times” response most young black men give.

“In my estimation, too frequently for a law-abiding citizen,” he says. “I know my rights and haven’t broken any laws.”

In March, Rollins joined Cop Watch, a national network of individuals dedicated to documenting police abuse. Saturday, he attended a training in Roxbury conducted by experts on video recording police, including National Lawyers Guild attorney Oren Numni and ACLU Massachusetts staff attorneys Sarah Wunch and Carlton Williams.

Cop Watch now has a smart phone application that enables people to upload video to a website as it’s being recorded, ensuring that even if police officers confiscate the phone, video evidence of police misconduct will not be lost.

Saturday’s training, which drew about 50 participants to the First Church of Roxbury, focused on how to record and interact with police officers safely.

Wunsch noted that the ACLU’s successful defense of attorney Simon Glick, who was arrested for using his cellphone to video record a police officer who was beating a suspect, established a sound legal precedent for video recording police.

Police charged Glick with illegal wiretapping, disturbing the peace and aiding the escape of a prisoner. It is illegal to record audio of police officers without their knowledge. But Glick, who used his cell phone in plain view, beat the charges.

“We said the First Amendment protects the right to observe and gather information on what our government is doing and share that with other people,” Wunsch said.

But Wunsch noted that it is important for people recording police officers to maintain a safe distance, so as not to interfere with an officer’s ability to make an arrest.

“Don’t get in the way of what they’re doing,” she said.

Much of Saturday’s training focused on the basic constitutional rights civilians have when confronted by law enforcement. As Williams explained, police can question individuals, but do not have the power to detain them unless they have a reasonable, articulable suspicion that a person has committed a crime or is in the process of committing a crime.

“You can ask, ‘Am I being detained?’” Williams said. “If the answer is ‘No,’ you can just walk away.”

If an officer has a reasonable, articulable suspicion, he can detain a person and conduct a pat-down frisk to make sure the suspect is not carrying a weapon.

“Generally, this is supposed to be for their own protection,” Williams said of the police frisk. “You still don’t have to talk to them, but they have the right to detain you.”

While teens complain police routinely go through their pockets and search their backpacks, Williams noted that searches based on ”reasonable suspicion” are illegal.

“They can only pat you down,” he said. “They will go into your pockets, but it’s unconstitutional.

That’s because police must have probable cause to arrest before conducting a search of a suspect’s pockets, bag, or car.

“They can only search for things that are related to the thing you are being arrested for,” Williams said.

Nevertheless, if a search turns up illegal items not related to the initial cause for arrest, the suspect can still be charged for possession of those items, Williams added.

To avoid illegal searches, Williams advised participants in the training to clearly state their refusal to be searched.

“Police officers will say, ‘You don’t mind if I look around in your car,’” Numni said. “You can say, ‘I don’t consent to a search.’ It’s important to say that, because a lot of things can be construed as consent.”

Williams and Numni also advised the audience members to avoid any physical confrontation with police officers.

“The best thing to do is to verbally resist and physically comply,” Williams said.

Seneca Joyner, an organizer with the Black Lives Matter movement and a convener of Saturday’s training, said the event was designed to help empower people to protect each other from police abuse.

“We want to make sure that when police encounter people on the street, people are protected from acts of aggression and misconduct,” she said. “The be-all and end-all isn’t getting video. Having the knowledge and presence to be there and support people is what’s important.