Testimony is to begin on Monday in the trial of a former Dallas police officer who claims she killed an unarmed black man after entering his apartment by mistake.

Amber Guyger is accused of murdering Botham Jean last year in a case that inflamed racial tensions and suspicion of the authorities in a Texas city with a long history of deadly contact between police and civilians.

Jury selection took more than a week, with about 4,000 summonses issued and hundreds of potential jurors questioned. Guyger’s lawyers argued she cannot receive a fair trial in Dallas because of “media hysteria” and public comments by officials about the shooting. They asked to move the trial to one of several nearby counties – a request the judge, Tammy Kemp, denied.

Seemingly fearful of public unrest, the Dallas police department told its officers last month that they could not request additional time off during the trial. There were street protests and angry scenes at a city council meeting after Jean’s death.

A Dallas civil rights group, the Next Generation Action Network, plans to hold a rally outside the courthouse on Monday.

The head of the Dallas police association called for the trial to be delayed on the basis that resources will be stretched by the city hosting the state fair of Texas, a suggestion that Lee Merritt, a lawyer for Jean’s family, described on Twitter as “absurd and contemptible”.

Guyger, who is white, had finished work on the evening of 6 September last year but was still in uniform when she parked at her apartment building. Jean, a 26-year-old accountant, lived on the floor above her.

In Guyger’s telling, she parked on the wrong floor after a long and tiring shift and walked into a dark apartment directly above her own, where she encountered Jean and thought he was a burglar. The 31-year-old claims she gave Jean verbal commands that were ignored. She then fired twice, fatally striking him with a bullet to the chest.

“If it was a white man would it have been different? Would she have reacted differently?” Allison Jean, the victim’s mother, said on the local station KXAS last year.

The family of Jean, who was born in St Lucia and was active in his local church, have filed a civil lawsuit that questions how Guyger could have missed various details telling her she was in the wrong apartment, such as signs, door numbers and a red floor mat outside the door. The lawsuit alleges she killed Jean “without any warning” as he got up from his sofa.

It also claims Guyger’s conduct reflects inadequate training and fits the department’s “pattern, practice, history and custom of using excessive force against minorities”, citing examples of recent fatal shootings by Dallas police.

Botham Jean pictured in 2017. He would have been 28 on 29 September. Photograph: Jeff Montgomery/AP

Activists and Jean’s family accused police of conducting a biased investigation in the immediate aftermath of his death, treating it akin to an officer-involved shooting of a suspect rather than a civilian killing an innocent victim. It was made public that marijuana was found in Jean’s apartment, which his supporters argue was an attempt to smear him.

An arrest warrant – which appears to rely heavily on Guyger’s version of events – was not issued until three days after the shooting, by which time Dallas police had handed the investigation to Texas rangers. Guyger was initially charged with manslaughter and fired two weeks later. A grand jury indicted her on a murder charge in November.

Guyger was a Dallas police officer for more than four years. She was previously cleared of any wrongdoing after shooting a suspect, who survived, in May 2017. Jean’s lawyers will attempt to depict her as having violent tendencies given that incident and aggressive quotations and memes she allegedly posted on social media, including: “People are so ungrateful. No one ever thanks me for having the patience not to kill them.”

Guyger’s lawyers are expected to argue that Jean’s death was a tragic accident and that – however misguidedly, given the location – she was acting in self-defense while fearing for her life and using lethal force in a context that is permissible under Texas law. Establishing whether Jean’s door was locked will probably prove important.

A recording of the 911 call made by Guyger was leaked to the local station WFAA in April. Sounding panicked and tearful, Guyger tells the dispatcher: “I’m an off-duty officer. I thought I was in my apartment and I shot a guy thinking he was … thinking it was my apartment … I’m fucked. Oh my God, I’m sorry … I’m going to lose my job.” She repeats the phrase “I thought it was my apartment” more than a dozen times.

A foundation created in Jean’s honor to expand on his missionary work is planning to hold a launch event in Dallas on 29 September, which would have been his 28th birthday.