San Francisco is exploring, once again, whether to arm police officers with stun guns in an effort to better subdue suspects and decrease shootings, with a working group set to present its findings Wednesday to the city Police Commission.

Proposals to acquire the electric shock weapons have been repeatedly defeated over the past decade, making the San Francisco Police Department the last major city force in the country without them, even though the police officers’ union wants access to them.

But this time, the focus of the debate has shifted.

The main concern in the past were deaths around the country associated with being shocked, but the question now being pressed by critics is whether the devices are effective enough — and what that means for an officer and a subject in an escalating, dangerous encounter.

“Their utility is really limited,” said John Burton, a Pasadena attorney who has represented plaintiffs in an estimated 30 lawsuits involving the weapons and who plans to make a presentation to the Police Commission, which will not hold a vote on the issue on Wednesday.

He noted that stun guns — which are typically Taser-brand weapons made by Arizona’s Axon — shoot two dart-like electrodes that are supposed to strike a person, with a current between the electrodes then incapacitating them. Thick clothing or a backpack can get in the way.

“You got to get two darts to land, and it’s got to be a good spread,” Burton said. “You have to be more than 7 feet away, but after 15 feet, the shot becomes impossible. The darts aren’t parallel and it’s just so easy to miss with that second dart.”

Some San Francisco police officers, though, want another use-of-force option, even if they might only rarely turn to it. Former Chief Greg Suhr was a Taser proponent, suggesting the devices could have averted the fatal, video-recorded shooting of Mario Woods in the Bayview neighborhood in December 2015.

Woods, a suspect in a stabbing who was allegedly still carrying a knife, was shot by several officers as he ignored commands and shuffled slowly along a sidewalk. The officers, whose actions are still under investigation, had failed to subdue him with beanbag blasts and pepper spray.

Police Chief Bill Scott, who took command in January, has said he supports Tasers, a view shared by the officers’ union. Martin Halloran, the union president, said officers needed more less-lethal options, especially after the Police Commission passed a more restrictive use-of-force policy in December emphasizing the sanctity of life.

“We have the least amount of less-lethal options available to us now more than ever before,” Halloran said. “Give us the tools needed to do our job and do it efficiently.”

Some experts, though, said a Taser might not have worked on Woods, who was wearing a puffy jacket.

“My biggest concern as a cop is a cold weapon — a weapon that is not doing what it is supposed to,” said Michael Leonesio, a retired Oakland officer who oversaw the department’s roll-out of stun guns and who is also presenting to the Police Commission. “The officer still thinks it works, it still fires the cartridge, but it doesn’t take the subject down. So now what happens?”

The presentation by the working group comes as part of the Police Commission’s effort to implement a slate of recommendations made by the U.S. Justice Department in the wake of the Woods shooting.

While the Justice Department said the city “should strongly consider deploying” stun guns, the report also recommended that the department and the commission work with stakeholders and community members to make “an informed decision.”

Tasers are used by thousands of police forces around the country and have been scrutinized for years. A Justice Department study released in 2011, which looked at hundreds of cases in which people died after being stunned, recommended that police avoid shocking suspects repeatedly. Most of the deaths were linked by authorities to underlying health problems, drug use or other issues.

Axon is now pushing a Taser that generates a weaker current than past models. Steve Tuttle, a company spokesman, said the lower voltage does not affect an officer’s ability to use the weapon successfully, though some experts disagree.

A Los Angeles Times examination of police data found that at least eight of 36 people shot by officers in 2015 were wounded or killed “during encounters in which officers said they tried to use a Taser without success.”

The newer Taser model was released in 2013. According to the newspaper, while Tasers failed to subdue subjects in 35 percent of deployments in 2011 and 2012, the figure was 40 percent in 2013, 36 percent in 2014 and 47 percent in 2015.

Tuttle said Los Angeles had tracked each trigger pull, when most law enforcement agencies look at the entire incident when measuring success.

He noted that officers can try to fire a second Taser or use the device in “drive stun” mode, pressing it against a person to gain compliance. In looking at entire incidents, he said, agencies see a success rate between 84 and 94 percent .

Leonesio estimated that during his time in Oakland, Tasers failed about a third of the time — and that was with the older, stronger model. While officers can train for weapons failure, he said, it’s difficult with Tasers because the officer may be left in a dangerous position near the subject.

An officer might feel compelled to escalate to using lethal force, he said, or to shock a person repeatedly.

“I’m not condemning the weapon,” Leonesio said. “There is a place for it. But because of the output that they have now and because of all the research that has been done now and because of what we know about the weapons now, if I was in San Francisco’s shoes, I wouldn’t do it. It would not be a high priority.”

Tuttle said Taser was able to introduce a less-powerful model because technology had progressed enough for the weapon to be “more efficient using less power.” Burton, the plaintiffs’ attorney, said the move was a response to lawsuits filed against the company.

In the process, he said, Axon has “gone into overdrive with warnings” intended to shield the company from liability.

“Don’t do it on a hard surface, don’t tase somebody with a heart condition, or with asthma,” Burton said. “Well, how are you going to know that? These are impossible if the police are using them in dynamic, fight-type situations.”

Police Commissioner Sonia Melara, who heads the Taser working group, said commissioners won’t vote on whether to equip officers with Tasers until they hold at least two community meetings. The city has not estimated the cost of obtaining Tasers.

Vivian Ho is a San Francisco Chronicle staff writer. Email: vho@sfchronicle.com Twitter: @VivianHo