Kate Steinle’s shooting death on a San Francisco pier in July 2015 by a man who had been deported multiple times escalated quickly from a crime to the subject of a nationwide furor over illegal immigration.

Donald Trump used Steinle’s death to fuel his campaign for president, branding her killer, Jose Ines Garcia Zarate, an “animal” and declaring that the shooting showed the need for a wall on the Mexican border.

In San Francisco, anger at Sheriff Ross Mirkarimi for his decision to release the jailed Garcia Zarate about 10 weeks before the shooting contributed to his 2016 re-election defeat. Mirkarimi cited San Francisco’s sanctuary city law in declining to notify federal immigration officials that he was about to release an undocumented Mexican with a criminal record.

The Trump administration has invoked Garcia Zarate and the slaying in its effort, unsuccessful so far, to strip federal funds from cities and states that refuse to take part in immigration enforcement. The House of Representatives, meanwhile, passed Kate’s Law, which would increase prison sentences for immigrants who, like the shooter, re-enter the U.S. after deportation.

All of that is supposed to be off the table for the jury that convenes Monday in San Francisco Superior Court, for opening statements in a trial scheduled to last seven weeks. Jurors will be instructed, instead, to consider only the evidence they hear in court on a single, crucial question: Did Garcia Zarate shoot Steinle intentionally, or was it an accident?

If Garcia Zarate, who has admitted firing the fatal shot, is found to have aimed at his victim, or at a group of people on the pier that night, he will be convicted of second-degree murder, punishable by 15 years to life in prison, and an additional 25 years for lethal use of a gun.

If jurors decide the killing was unintentional but Garcia Zarate was grossly negligent, he will be guilty of involuntary manslaughter, punishable by two to four years in prison — though previous drug convictions could add 13 more years to his term. And if, as his lawyers contend, he fired the gun accidentally, after finding it wrapped in a T-shirt under a bench and unintentionally setting it off as he unwrapped it, he must be acquitted.

During two weeks of jury selection, Judge Samuel Feng repeatedly told prospective jurors that immigration, sanctuary cities, gun control and their political views should not enter into their deliberations.

Lawyers on both sides conveyed much the same message but tried to put their own spin on the Trump connection. Assistant District Attorney Diana Garcia asked whether any jurors were so angry at Trump that they would be unable to convict Garcia Zarate, while Matt Gonzalez, chief attorney in the public defender’s office, asked whether they could return a verdict that the president would dislike.

Whether 12 ordinary citizens can ignore as jurors what they know as human beings is another question.

“We are all human, and it’s nearly impossible to come in with a clean slate,” said Laurie Levenson, a criminal law professor at Loyola Law School in Los Angeles and a former federal prosecutor. “And you have to think about whether you really want jurors who don’t have knowledge or opinions. ... The best that the law hopes for is that people will decide this case just on its facts and not on their prejudices.”

Sometimes, asking jurors to ignore something merely piques their curiosity, said Hadar Aviram, a criminal law professor at UC Hastings in San Francisco.

“Social science tells us that people’s experiences, people’s demographics and people’s histories come with them to decide questions of fact,” Aviram said. On the other hand, she said, jurors might be able to put their views aside while grappling with issues of ballistics and forensic evidence.

Steinle, 32, was shot in the back on July 1, 2015, as she walked along Pier 14 near the Ferry Building with an arm around her father. Garcia Zarate, who turned 45 Friday, had been released from San Francisco custody nearly three months earlier.

He had been deported to Mexico five times since first entering the U.S. as a juvenile. Convicted of felony re-entry and sentenced in 2011 to 46 months in federal prison, he was released in March 2015. Then, instead of being deported a sixth time, he was transferred by federal authorities to San Francisco to face an old marijuana charge.

But city prosecutors dropped the charge, and Mirkarimi’s office released Garcia Zarate three weeks after he’d arrived in the city without notifying federal agents. The sheriff relied on his interpretation of a San Francisco ordinance barring cooperation with immigration officers unless an inmate in local custody has a serious criminal record or the agents have a warrant.

The gun used to kill Steinle had been stolen from the car of a U.S. Bureau of Land Management ranger four days earlier. Garcia Zarate, who was homeless, has not been charged with stealing it. In a separate case, a federal magistrate has allowed Steinle’s parents to sue the federal government for negligence over the ranger’s actions, but has rejected their claims against Mirkarimi and the city for Garcia Zarate’s release, finding that they violated no laws.

Prosecutors plan to call the ranger as a witness in the trial. Gonzalez says he doesn’t expect to call Garcia Zarate to the stand.

“We’re dealing with someone with about a second-grade education, who’s got some cognitive challenges, some health issues,” Gonzalez said in an interview. But he said the jury will hear evidence of a police interview with his client in which officers elicited potentially damaging admissions — which, Gonzalez said, were factually inaccurate.

“The police got him to say he was 5 feet away from Kate Steinle when the gun went off,” but the evidence will show that Garcia Zarate was sitting 90 feet away and fired a bullet that bounced off the pavement 12 feet from where he was standing, then ricocheted into the victim, Gonzalez said.

It was a “freak accident,” the defense lawyer said.

Gonzalez said officers also got Garcia Zarate to say he walked past the bleeding Steinle without trying to help, even though he had actually headed in the opposite direction after the shooting.

Jurors will hear competing expert witnesses about the gun, a .40-caliber SIG Sauer P226. Prosecutors contend the pistol’s firing mechanism was in a position that would have required a conscious, deliberate action to pull the trigger. Gonzalez said defense witnesses will testify that it was set in hair-trigger mode and had no safety device, and that trained law enforcement officers had accidentally fired the same model firearm.

The 12 jurors range in age from 24 to 57. Gonzalez said three are immigrants; jurors’ occupations include flight attendant, software engineer, nurse, marketing accountant and health economist; and they live in a variety of neighborhoods, from Visitacion Valley, Bernal Heights and the Excelsior to the Mission District, Russian Hill and Nob Hill.

Defense lawyers in emotionally laden, high-publicity cases often seek to transfer the trial to another county. Gonzalez made no such request in this case.

“Things that happened in San Francisco ought to be tried here,” he said. The city is large enough, and enough time has passed since the shooting, he said, “that we ought to be able to have fair and impartial jurors.”

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com Twitter: @egelko