The Chronicle’s D.A. Tuesday is back — this week with candidate Nancy Tung.

We’re bringing you the biographies and policy proposals of each of the four candidates for San Francisco district attorney over four Tuesdays. The November election marks the first time in more than a century that the incumbent isn’t running after District Attorney George Gascón declined to see re-election.

That means the race is wide open, and voters need to do their homework to assess the qualities of the four hopefuls. Last week, we told you about Leif Dautch, a deputy attorney general for the state. This week, it’s Tung, a former prosecutor in the office she hopes to lead who now works for the district attorney in Alameda County.

She grew up in Baton Rouge, La., and jokes that her family was “one of six Chinese families in the whole state.” They moved to California when she was 10, and Tung graduated from UC Berkeley before attending law school at Georgetown in Washington, D.C.

She worked in the state attorney general’s office before an 11-year stint in the San Francisco district attorney’s office. She recently transferred to the Alameda County district attorney’s office, citing low morale, high turnover and frustration with Gascón’s leadership.

She said she’d give her former boss a B-minus and noted he’d never tried a case when he was appointed by then-Mayor Gavin Newsom. He had served as police chief until the appointment.

“I’ve been a prosecutor for 18 years — does that make me qualified to be police chief?” Tung quipped.

Gascón’s office has said it won’t be commenting on the race.

Tung is arguably the most conservative candidate — by San Francisco standards, of course. She believes the district attorney needs to be tougher on crime and serve on the board of Stop Crime SF, a group of city residents that seeks to hold the city’s often lenient criminal justice system accountable.

Tung, 44, and her husband are raising their 21-month-old son, Malcolm, in the city’s South of Market district, and she calls her toddler “the best thing I’ve ever done with my life.”

Here are the highlights of my talk with Tung. To hear the entire interview, listen to the latest episode of our podcast, “San Francisco City Insider,” at www.sfchronicle.com/insider.

On the city’s broken mental health care system:

The recent high-profile case of a mentally ill homeless man who allegedly assaulted a woman outside her home near the Embarcadero, saying he needed to save her from robots, has highlighted the city’s flawed mental health care system.

A Superior Court judge initially released him from jail to a treatment program, and a transcript shows the prosecutor didn’t try very hard to persuade the judge otherwise. Tung said it’s clear the man should have been behind bars from the start and said San Francisco’s jails are progressive and full of good therapy, education and drug treatment programs.

“We need to support those functions within the jail instead of saying, ‘Well, the only thing we can do is put somebody in jail or put them in an unlocked facility where they might get treatment and walk away,’” she said. “We shouldn’t be sacrificing public safety.”

Tung said San Francisco should also provide conservatorship for more mentally ill people who are too ill to know they need help. A recent report showed the city is conserving far fewer people per capita than neighboring counties, partly because the city has fewer treatment beds than it used to despite a $12.3 billion annual budget.

“If we can use what tools we have available already, we can move toward making San Francisco a more humane place and not waiting for people to get involved in the criminal justice system in order to get them help,” Tung said.

On the scourge of open-air drug dealing:

Tung supports the federal government’s recent crackdown on open-air drug dealing in the Tenderloin because she said it’s obvious the city hasn’t been able to get a handle on the crime, which is damaging life for residents.

“The open-air drug dealing has affected the people who live there in the Tenderloin every single day,” she said. “You have kids walking around who see people with needles in their arms every day and drug dealers on the corner. ... We have utterly failed in terms of public safety.”

She said it’s hypocritical for San Francisco to say it’s a progressive city and yet allow low-income people, little kids and elderly people to be subjected to the Tenderloin’s drug infestation on a daily basis. She said it’s also sad the city lets drug users who are passed out in “a completely vulnerable state” just lie there on the sidewalk.

She said prosecutors need to go after dealers, and police should remove drug users from the streets and take them to drug treatment facilities.

On whether she would have charged the officers in the Mario Woods case:

Tung said she would not have charged the officers in the infamous 2015 case in which they formed a semicircle around Woods as he stood against a wall in the Bayview and fatally shot him. He was a suspect in a stabbing and had been spotted by officers holding a knife.

The shooting was captured on video and drew national outrage amid other police killings of African Americans. Gascón didn’t charge any of the officers involved, and Tung said she agrees with that decision.

“They put the facts out in a way that shows why it shouldn’t be charged,” she said. “It’s hard for the family of Mario Woods, but where we can focus these types of police-involved shootings is de-escalation.”

She said she supports the effort to train San Francisco officers on how to de-escalate heated encounters “rather than trying to force a prosecution into a fact pattern that doesn’t have the evidence to support a prosecution.”

On the city’s car break-in and property crime epidemic:

Tung said organized gangs that break into cars are proliferating, and prosecutors need to team up with other law enforcement agencies around the region to go after them.

“We don’t have criminals who stop at the county line,” she said. “We need to focus our efforts on breaking those rings ... so we don’t pick around the edges of the problem and prosecute one person at a time.”

On the rash of pedestrian deaths this year:

Tung said the district attorney should investigate and potentially prosecute drivers in traffic collisions that kill pedestrians or bicyclists as if they’re homicides.

She said the city should also exert pressure on Uber and Lyft to do a better job ensuring their drivers practice safe behavior.

Next week, D.A. Tuesdays will continue with Suzy Loftus, an attorney in the sheriff’s department and the presumed front-runner in the race.

San Francisco Chronicle columnist Heather Knight appears Sundays and Tuesdays. Email: hknight@sfchronicle.com Twitter: @hknightsf Instagram: @heatherknightsf