The official report into the police shooting of a man whose death sparked the 2011 riots is facing a new challenge from human rights investigators who say a virtual model of the shooting shows its main conclusion is wrong.

The shooting of Mark Duggan, 29, in Tottenham, north London, in August 2011, triggered the biggest riots in modern English history.

An investigation by the police watchdog found he was most likely shot while holding a gun that he was probably “in the process of throwing” away.

An illegal firearm was found over a fence and 14 feet (4.35 metres) from where Duggan fell. None of the police officers surrounding him saw it flying through the air.

Now work by Forensic Architecture, a London-based research organisation that uses modern technology to search urban areas for evidence, claims it was unlikely that Duggan was holding a gun when he came face to face with police.

They used the official accounts from officers and official records to recreate a virtual model of the scene. They say it allows people to experience what each officer could have seen throughout the incident, and their fields of vision.

Prof Eyal Weizman of FA said their work undermines the finding by the police watchdog, which was then called the Independent Police Complaints Commission. He said: “We generated a precise 3D model of the site within which we played the different scenarios proposed by the police officers involved as well as the accounts of the official IPCC investigation and the inquest, checking their plausibility.”

Weizman said if the gun had been tossed away, it would have been in the field of vision of officers.

“The model allowed us, for the first time, to give a depiction of what each of the police officers on site could have seen. We found that the conclusion arrived at by the IPCC, that Mark Duggan held the gun in his hand and threw it when he was shot, is incorrect,” Weizman added.

An inquest jury found the shooting to be lawful, and the police watchdog found no suggestion of any wrongdoing by the officer who shot Duggan, known only as V53.

On the day he was shot, police correctly believed Duggan was trying to obtain a firearm, which he did get from a criminal contact.

As he drove from east London, where he had collected the gun, towards Tottenham, Duggan was being followed by armed police, and became aware they were tailing him. The cab he was in was forced to stop by three Met police vehicles.

The time from when his cab stopped to when he was shot lasts around five seconds, a short period of time whose events are still subject to claim and counter-claim.

Once stopped, Duggan did not surrender but fled out of the cab on to a pavement. There, V53 shot him twice, once in the arm, and in the chest, believing Duggan was holding a gun.

Duggan was surrounded by officers, some of whom were just a few feet away, when he was shot.

FA is based at Goldsmiths, University of London and has investigated alleged human rights abuses around the world on behalf of clients such as the United Nations special rapporteur for counter-terrorism and human rights and Médecins Sans Frontières.

For their work on the Duggan case they were commissioned by the dead man’s family lawyers who were suing the Met.

The intention was their virtual model reconstruction could be an aid to the court if civil proceedings had continued.

The Met settled for an undisclosed sum running into the tens of thousands, without admitting liability, to the family of a man it was ruled was lawfully killed.

In 2014, an inquest jury concluded that Duggan threw the firearm from the cab when it was forced to stop, and it landed over the fence. The jury decided Duggan was not holding a gun when shot.

Weizman said: “We also found that inquest’s jury conclusion that Mark Duggan has thrown the gun before he exited the minicab, has problems with it, namely, our model showed that the gun would have travelled through the field of vision of several key witnesses that could have seen it.”

Weizman added: “We think that the right thing is for this case to be reopened.”

Stafford Scott, a community activist who has supported the Duggan family, said: “Had we had the FA model at our disposal during the inquest process the outcome would surely have been a different one.”

The officer who shot Duggan, V53, says he had an honestly held belief that he saw a gun in Duggan’s right hand and his right arm beginning to move. The officer feared that his life or that of his colleagues was in imminent danger.

The former Met firearms officer Tony Long, who supported V53, said the constant questions and long-running inquiries take their toll. He said: “You know you took the right action, but so much criticism is levelled at you.”

Long himself was tried and acquitted of murder after a different police shooting. He said: “None of us go out on an operation with the intention of shooting anybody.

“You have a fraction of a second for your decision-making process, made with emotion in a life-threatening situation. Then these armchair experts sit down and look at it in a ridiculous amount of depth and go over things, over and over, when you only had a split-second.”

There was no forensic link or DNA showing Duggan had touched the gun. He had touched a shoe box in which he had collected the firearm. The gun was not ready to fire.

The Independent Office for Police Conduct, which succeeded the IPCC, said it stood by its findings: “Our findings were based on a comprehensive investigation … We commissioned reports from a number of experts in the fields of pathology, DNA profiling, firearms and ballistics, fibre analysis, toxicology, pharmacology, finger and palm printing and bio-engineering.”

The IOPC said of FA’s findings: “If it was provided to us we would consider any compelling new evidence with the potential to affect our original findings.”

The Met said: “The actions of MPS officers surrounding Mr Duggan’s death have been subject to extensive forensic scrutiny through an inquest process which returned a verdict of lawful killing, as well as IPCC (now IOPC) independent criminal and misconduct investigations which found no case to answer for any officer involved.”