In 2011, Virginia police officer Stephen Rankin shot an unarmed man dead. Last year he did it again. The fight to get him convicted is the subject of a new film

Ken King is a veteran of the US navy. He worked for 25 years as a policeman in southern Virginia. After retiring at the rank of lieutenant, he took command of a military unit guarding the prison camp at Guantánamo Bay.

King does not, therefore, conform to the Donald Trump caricature of those who protest against killings by police officers. And yet King knows what he knows. He will tell you about a preventable error by police that had deadly consequences on two occasions. It may, in fact, be the most serious single institutional failing in US policing to come to light since Ferguson, Missouri, erupted into civil unrest in 2014.

The Guardian first reported in June last year that King, who then went unidentified, had warned senior commanders at Portsmouth police department about the dangers posed by one of the officers under his command. The officer was Stephen Rankin.

Officer Rankin was receiving too many complaints about his use of force, King told them, such as using his Taser to shock a 60-year-old grandmother during a dispute about her car being towed, and wrestling a 15-year-old girl to the ground in a routine confrontation.

“There are some people who come into law enforcement who are not suited for the job,” says King, who is softly spoken but intense. “Stephen Rankin was one of those people.”

Rankin had the capacity to “cause a riot at a church social,” as King puts it. “He could go to any event and it would just escalate out of control in some way.”

Previously reluctant to speak publicly, King agreed to be interviewed for a powerful documentary, which builds on the Guardian’s reporting, and airs on BBC2 on Wednesday.

King says he asked internal affairs investigators working for Portsmouth police chief Ed Hargis to look into the repeated complaints about Rankin’s excessive force, but the officer was allowed to continue policing the public. Later, after finding that Rankin was also falsely claiming overtime pay, King says he wrote to Hargis recommending the officer be fired from his job. He wasn’t.

Facebook Twitter Pinterest William Chapman was shot by Rankin in a Walmart car park. Photograph: BBC

Then, one evening in 2011, Rankin shot dead an unarmed young man while responding to a 911 call. One morning last year, he did it again.

“We missed an opportunity to get rid of this officer a long time ago,” says King. “And no one’s better off because we didn’t do that.”

Portsmouth is an old harbour and plantation town, part of the Tidewater region, about halfway down the Atlantic coast. More than half of its 96,000 residents are black. Its colonial heritage and contemporary culture mix curiously. US naval vessels are still repaired and upgraded at its vast 250-year-old shipyard, which was once a useful outpost for the British crown. It is also the birthplace of Missy Elliott, the rapper and producer. Rankin, like many men in the area, landed in Portsmouth with the US navy. As a 22-year-old raised in California, he had met Cori Johnson, a 17-year-old rebel from an evangelical Christian family. He proposed after six weeks. They married and had a daughter. She followed him across the US on his naval postings and waited while he was deployed as a military policeman to Kuwait, to aid the US war effort in Iraq.

Discharged in Portsmouth in 2007 after five years, Rankin decided to become a policeman. He was rejected by several departments for having used methamphetamine in his youth. “I did it ONE TIME when I was 16,” he complained later, on an online forum. But Rankin was eventually accepted at Portsmouth, a department with a strong military streak thanks to the local base.

Johnson told the documentary makers that as complaints from the public about his violence piled up, Rankin said they merely proved he was doing his job properly. He also became obsessed with a particular premise for a police officer opening fire on a suspect. He would return to this hypothetical constantly in conversations with colleagues, she said.

“Don’t you think you’d be justified in shooting somebody if they put their hand on their waistband?” he would ask.

Facebook Twitter Pinterest Chapman’s mother Sallie holding a vigil outside Walmart. Photograph: BBC

Rankin’s marriage began to deteriorate, and ended in divorce. King’s efforts to have Rankin removed from the streets were in vain. But on the evening of 23 April 2011, Rankin answered a 911 call reporting someone banging on the front door of an apartment building in Portsmouth’s historic Olde Towne area.

Kirill Denyakin, a cook from Kazakhstan who was living in the town, had been drinking too much while out with friends. Denyakin had ended up outside the apartment building in question, where he had been staying, and began rapping incessantly on the glass door. Footage from a dashboard camera in Rankin’s car shows the officer arriving in response to the 911 call and leaping over a grass verge. Seconds after he disappears from view, 11 gunshots are heard.

Photographs taken at the scene showed that Denyakin ended up with his jeans around his ankles. Friends suggested he had been urinating. Certainly he had no weapon. But Rankin claimed he had been forced to fire his gun repeatedly because the 26-year-old turned, charged toward the officer aggressively – and reached into his waistband.

“When I read his statement in the newspaper, that he had said ‘hand on the waistband’, a chill went up my spine,” said Johnson. “I realised this was not a standard line-of-duty shooting. I realised this was what he’d been waiting for.”

King adds: “I think you could have put 100 other officers in that same situation and you would not have had that same outcome.”

In those pre-Ferguson days, Rankin avoided criminal charges and the national spotlight. Denyakin’s family sued in the civil courts for $22m (£18m). After they rejected an offer of a small settlement, however, the jury at trial sided with Rankin, accepting his claim that he was forced to fire because he feared for his life, and awarding the family no damages. Denyakin’s mother, Yelena, went home distraught and empty-handed. Denyakin’s family had also come under attack in the comments section of the Virginian-Pilot, their local newspaper. “22 mil wont buy your boy back,” wrote one observer, under the username yourealythinkthat.

Facebook Twitter Pinterest Kirill Denyakin was shot within seconds of Rankin arriving at an apartment where an inebriated Denyakin was banging on the door. Photograph: Guardian Video

Most Americans, the commenter said, could not hope to earn such a sum in their entire career, “let alone a habitual drunk working as a hotel cook”. Speaking under oath six months and 246 comments later, Rankin admitted that he was actually yourealythinkthat.

The killing caused a diplomatic incident. Officials from Kazakhstan, a key central Asian ally for the US in post-9/11 conflicts, made their anger known to the State Department. Concerns were relayed to the authorities in Portsmouth, who also faced a furore over Facebook postings from the previous two years that showed Rankin, a firearms obsessive, referring to his gun container as “Rankin’s box of vengeance”.

Rankin was put on administrative duties, leaving him stuck behind a desk for the following two years and nine months, until things blew over. But then he was let out again.

“Not only was he told it was OK, but in his world, he was empowered by it,” Johnson says in the documentary. “It made him a hero. It made him a badass. Why give that up? Why stop?”

When a security worker at the town’s Walmart store called 911 early on 22 April last year to report a suspected shoplifting, the US was in a state of acute anxiety. It was only eight months since Michael Brown, an unarmed black 18-year-old, had been shot dead in Ferguson, and the aftershocks were still felt.

Virginia officer said 'This is my second one' after killing William Chapman Read more

Protests spread to major cities. A long-dormant debate about race and policing was forced back to the top of the domestic political agenda. And the discord was about to enter a second phase. In Baltimore, Maryland, 22-year-old Freddie Gray had just died of a broken neck after being driven around shackled in the back of a police van without a seatbelt. Demonstrations turned into clashes with police, rioting and arson.

It meant the country was already preoccupied by the in-custody death of a young African American man when Rankin took that early-morning 911 call and confronted 18-year-old William Chapman in the Walmart’s vast car park.

Rankin was not in a good mood. “I hate this job,” Rankin, who was 34, had told a colleague in a mobile message about an hour earlier. “Seen too much bad and not enough good.” The colleague brushed aside his complaints, but Rankin insisted. “The city sucks, but so does the rest of the world. People are just bad,” he said. He made an allusion to the condemned biblical cities of Sodom and Gomorrah.

Then, as Rankin tried to detain Chapman, the 18-year-old defied him. “Take your hand out your pocket,” Rankin said, as they began to struggle at Rankin’s squad car. “Take your hand out your pocket.” Rankin drew his Taser, which had an in-built camera that recorded their exchange. “You’re not gonna Tase me, cos you’re not gonna arrest me for nothing,” Chapman told him, before knocking the Taser to the ground. The pair split apart and stood face to face, separated by the car.

What happened next is sharply disputed. A Walmart security worker, a young black man named Gregory Provo, said Chapman took a “jab step” – an upper-body jerk meant to make an opponent flinch. “He never charged, he just made a gesture,” said Provo. Rankin and some white builders working nearby claimed that Chapman advanced towards the officer. No one, however, disputes that Chapman was unarmed.

Facebook Twitter Pinterest Stephen Rankin. His ex-wife says Rankin would talk about a hypothetical premise in which it would be justified to shoot a suspect. Photograph: BBC

Rankin fired his Glock pistol twice in quick succession. Chapman was struck in the face and chest. The 18-year-old died almost instantly, becoming one of 306 African-Americans killed by police last year, as recorded by an award-winning Guardian project, called The Counted.

According to King, the retired lieutenant, it needn’t have happened.

“He was given chance after chance,” King says of Rankin. “Sometimes tragic things happen that can’t be prevented, and there was no chance to try to avoid it. But in this case, it could have been avoided.”

After his second killing, Rankin faced a drastically different situation. The number of officers charged with crimes for deadly shootings in 2015 across the country was three times higher than in recent years. Meanwhile, in Portsmouth, the white, male Republican prosecutor who oversaw Rankin’s avoidance of charges for killing Denyakin was gone. In his place was Stephanie Morales, a recently elected black Democrat, just 31 years old.

In August last year, Morales announced that she would pursue criminal charges against Rankin for killing Chapman. The following month, a grand jury returned an indictment of first-degree murder – still a highly unusual charge for a police shooting. Rankin was also terminated from his job.

The documentary follows Rankin and the Chapmans through the murder trial, which spanned two sweltering weeks in summer. As a steady stream of controversial shootings by police continued to flow across the US, extensive security measures were installed at Portsmouth courthouse, where officers stationed on the roof scanned the area for potential danger.

Rankin was protected by a coterie of armed deputies dressed like soldiers. “We had some pretty credible threats on our lives,” said his second wife, Dawn.

Funded by her friends and neighbours, Yelena Denyakin flew back to Virginia to see Rankin in the dock. Jointly determined to see him punished this time, Denyakin and Sallie Chapman, William’s mother, forged an unlikely partnership “Rankin didn’t just kill my son,” said Denyakin. “He destroyed our whole family.”

“If I get justice, then we get justice together,” said Chapman.

Unshaven and dishevelled, the former officer gave his first and only public interview for the film, breaking an unspoken omertà among officers that typically follows deadly encounters. “Having to shoot someone,” said Rankin, is “not as easy as it looks in the movies.”

Facebook Twitter Pinterest The victim’s mothers Yelena Denyakin and Sallie Chapman before Rankin’s trial. Photograph: BBC

While offering sympathy to the Chapmans, Rankin remains convinced of his propriety, and aggrieved at his treatment, which he contrasts with the “three weeks and a medal” – paid leave and a commendation for bravery – that he claims ordinarily would be expected. “I did exactly what I was trained to do,” said Rankin. “I did my job, and I really feel like I’m being punished for doing exactly what I was supposed to do.”

Pre-trial wrangling resulted in rulings that jurors would not hear about Rankin’s first deadly shooting. Nor, though, would they learn of childhood offences committed by Chapman, who was sent to a juvenile prison after bringing to school a cigarette lighter styled like a pistol.

Inside the courtroom, America’s troubling racial divide played out in miniature. Morales was joined in prosecuting Rankin by her black deputy; Rankin’s attorneys were white. While one half of the public gallery filled each morning with Rankin’s white supporters, Chapman’s family filled the other side with black friends and activists. Even eyewitnesses and jurors divided along racial lines.

The days were thick with tension. “He and his wife are sitting there peacefully,” Yelena Denyakin said during one sunny lunch break. “Soon their peace should come to an end.”

Morales, styled as naive by local media for daring to charge an officer with murder, was fighting for her political future. She faced off aggressively against attorney James Broccoletti, a grizzled veteran defending Rankin after getting a man cleared of murder despite his fingerprints being found on bags the body was wrapped in.

Rankin, facing a potential life sentence if convicted, was clinging to his freedom, to his chances of working again as a police officer – and to his right to ever again own a gun.

“I believe it’s not just me that’s on trial,” said Rankin. “I believe it’s all American police officers.”

• Unarmed Black Male will be broadcast on BBC2 at 9pm on Wednesday 2 November