Kevin Hutchinson-Foster was convicted today of passing the gun to Mr Duggan after a retrial at the Old Bailey. A jury previously failed to reach a verdict at Snaresbrook Crown Court.
During the trial the court heard that Mr Duggan collected the BBM Bruni Model 92 handgun just 15 minutes before he was shot dead on August 4 2011.
The 29-year-old's death in Ferry Lane, Tottenham, north London, sparked riots that swept across London and other English towns and cities.
Hutchinson-Foster, 30, had denied a charge of “selling or transferring a prohibited firearm” to Mr Duggan between July 28 and August 5, 2011.
A jury at Snaresbrook Crown Court could not reach a verdict after a trial last year, but after a retrial at the Old Bailey, a jury of seven women and five men today convicted him by majority verdict.
During both trials armed police, who gave evidence anonymously, described how they opened fire on Mr Duggan because they saw him get out of the cab holding a loaded gun.
The officer who shot Mr Duggan twice - once in the chest and once in the arm - said he fired because he thought he was going to shoot him and his colleagues.
Mr Duggan, who was under police surveillance that day and the day before, had gone in the minicab to Leyton, east London, where he collected the gun in a shoebox from Hutchinson-Foster, before continuing to Tottenham.
The cab was pulled over by armed police in four unmarked cars in a “hard stop”, and as Mr Duggan got out clutching the gun, he was shot.
During the trial, prosecutor Edward Brown QC told the court: “The death of Mr Duggan has been regarded as the event that sparked the riots in north London, which then spread across London and then to other cities and which attracted widespread publicity in the United Kingdom and abroad.”
But he told the jury it was not their task to decide the “rights and wrongs” of Mr Duggan's shooting, which will be examined at the inquest into his death, set to take place in September.
Hutchinson-Foster has admitted using the same gun to beat barber Peter Osadebay at a barber's shop in Dalston, east London, just six days before Mr Duggan's death. The defendant claimed this was why his DNA was found on the gun when it was retrieved from Ferry Lane on August 4, along with traces of Mr Osadebay's blood.
The gun was found five metres from Mr Duggan's body, on a grass verge behind railings.
The shoebox, found in the minicab, had both Mr Duggan's and the defendant's fingerprints on it, while mobile phone evidence showed they were in contact with each other in the run up to the shooting.
But Hutchinson-Foster, a cannabis user with convictions for possession of cocaine and heroin with intent to supply, claimed Mr Duggan had wanted his help to sell some cannabis.
He said he collected the firearm from someone else so he could beat Mr Osadebay on July 29, but had returned it on the same day.
The jury heard testimonies from the CO19 officers who shot Mr Duggan.
The man who opened fire on the 29-year-old, known only as V53, said he was sure Mr Duggan was holding a handgun.
He shot Mr Duggan once in the chest, then a second time, hitting his right bicep. Afterwards he went to treat a fellow officer who had been hit by a stray bullet, but realising it had hit his radio, started giving CPR to Mr Duggan.
Other officers told the court Mr Duggan was hiding something in his hand when the cab was stopped and saw him raise what appeared to be a gun as he got out.
But the minicab driver, who said he would never be able to wipe the incident from his mind, said he did not see Mr Duggan raise his arms towards officers.
After the verdict, the jury was shown CCTV of the incident at the barber's shop on July 29, 2011, where Hutchinson-Foster threatened Peter Osadebay, then returned and used the gun to beat him.
Hutchinson-Foster previously pleaded guilty to a charge of possession of a firearm with intent to cause fear of violence, and one of assault occasioning actual bodily harm.
“The attack upon Mr Osadebay was described by a male witness as a 'pistol whipping' by the defendant and the witness described how they were scared and frightened that he might fire some shots at the members of the public,” said Mr Brown.
He said another witness described being genuinely scared, and told police his girlfriend refused to go back to the salon.
“When police officers arrived they found Mr Osadebay injured, slipping in and out of consciousness, and in fact at one point lost consciousness.
"The Crown's case has always been that the defendant, if he did obtain it (the gun) between the two visits to the hair salon, kept hold of it until August 4."
The court heard that Hutchinson-Foster is in prison serving a 54-month sentence for possession of cocaine and heroin with intent to supply. That sentence is due to finish in December.
He had been released from prison after a previous sentence in April 2011, and committed these offences while on licence, Mr Brown said.
The case was adjourned until 11am on February 26, when Hutchinson-Foster will be sentenced.
Alison Saunders, CPS London chief crown prosecutor, said: "The CPS proceeded with this prosecution based on evidence that Kevin Hutchinson-Foster had transferred a gun to Mark Duggan hidden in a shoe box in Tottenham on 4 August 2011.
“He had already lied about possessing the same gun and beating a person with it six days earlier, despite strong evidence linking him to that offence.
”He eventually pleaded guilty to those charges and today a jury found him guilty of this further offence.
“We are committed to tackling the menace of gun crime and will continue working closely with the police to pursue and prosecute those who supply or transfer the weapons that have caused terrible pain to so many families.
”This conviction sends a strong message that gun crime and violence will not be tolerated in London.“
Chief superintendent Dean Haydon, from Scotland Yard's Trident Gang Crime Command, which tackles gang and gun crime, said: ”Kevin Hutchinson-Foster has today been found guilty of supplying a firearm to Mark Duggan.
“This is in addition to the two other offences he has already pleaded guilty to, namely assault and possession of a firearm with intent to cause fear.
”There is an ongoing IPCC investigation into the death of Mark Duggan and the circumstances of his death will be a matter for the coroner at a later date.
“The Trident Gang Crime Command supported by specialist firearms officers, lead the Met's response to the criminal use of firearms in London.
”As a result of the hard work, commitment and dedication of our officers, London has seen a sustained 20 per cent reduction in gun crime over the past four years, and last year alone the Metropolitan Police Service seized over 340 firearms and large quantities of ammunition.
“The Kevin Hutchinson-Foster trial has primarily been about the supply of an illegal firearm and I welcome the verdict of the jury in this case today.”