Alex Nieto was 28 years old when he was killed, in the neighbourhood where he had spent his whole life. He died in a barrage bullets fired at him by four San Francisco policemen. There are a few things about his death that everyone agrees on: he was in a hilltop park eating a burrito and tortilla chips, wearing the Taser he carried for his job as a bouncer at a nightclub, when someone called 911 on him a little after 7pm on the evening of 21 March 2014. When police officers arrived a few minutes later, they claim Nieto defiantly pointed the Taser at them, and that they mistook its red laser light for the laser sights of a gun, and shot him in self defence. However, the stories of the four officers contradict each other, and some of the evidence.

On the road that curves around the green hilltop of Bernal Heights Park there is an unofficial memorial to Nieto. People walking dogs or running or taking a stroll stop to read the banner, which is pinned by stones to the slope of the hill and surrounded by fresh and artificial flowers. Alex’s father Refugio still visits the memorial at least once a day, walking up from his small apartment on the south side of Bernal Hill. Alex Nieto had been walking on the hill since he was a child: that evening his parents, joined by friends and supporters, went up there in the dark to bring a birthday cake up to the memorial.

Refugio and Elvira Nieto are reserved people, straight-backed but careworn, who speak eloquently in Spanish and hardly at all in English. They had known each other as poor children in a little town in central Mexico and emigrated separately to the Bay Area in the 1970s, where they met again and married in 1984. They have lived in the same building on the south slope of Bernal Hill ever since. She worked for decades as a housekeeper in San Francisco’s downtown hotels and is now retired. He had worked on the side, but mostly stayed at home as the principal caregiver of Alex and his younger brother Hector. In the courtroom, Hector, handsome, sombre, with glossy black hair pulled back neatly, sat with his parents most days, not far from the three white and one Asian policemen who killed his brother. That there was a trial at all was a triumph. The city had withheld from family and supporters the full autopsy report and the names of the officers who shot Nieto, and it was months before the key witness overcame his fear of the police to come forward.

Nieto died because a series of white men saw him as a menacing intruder in the place he had spent his whole life. They thought he was possibly a gang member because he was wearing a red jacket. Many Latino boys and men in San Francisco avoid wearing red and blue because they are the colours of two gangs, the Norteños and Sureños – but the colours of San Francisco’s football team, the 49ers, are red and gold. Wearing a 49ers jacket in San Francisco is as ordinary as wearing a Saints jersey in New Orleans. That evening, Nieto, who had thick black eyebrows and a closely cropped goatee, was wearing a new-looking 49ers jacket, a black 49ers cap, a white T-shirt, black trousers, and carried the Taser in a holster on his belt, under his jacket. (Tasers shoot out wires that deliver an electrical shock, briefly paralysing their target; they are shaped roughly like a gun, but more bulbous; Nieto’s had bright yellow markings over much of its surface and a 15-foot range.)