The mother of Mark Duggan today won an appeal against a jury's finding that her son was "lawfully killed" after being shot by a police marksman.

A Court of Appeal judge ruled today that Mr Duggan's family had an "arguable case" and that the matter should go to full appeal.

Mr Duggan's death sparked nationwide riots after he was shot by a police marksman in August 2011.

In January 2014 an inquest jury found Mr Duggan, 29, was lawfully killed in in Tottenham, north London, despite being unarmed.

But today during a leave to appeal hearing Mr Justice Sales judge ruled the questions put by the coroner to the inquest jury were "framed too narrowly" and that they should have been asked to consider if it was 'reasonable' for the officer, V53, to open fire even though he was mistaken about whether Duggan was armed.

Now Mr Duggan's family want an investigation into whether there were "objective" reasons for believing Mr Duggan posed a threat to the police officers.

In 2011, the minicab Mr Duggan was travelling in was intercepted by armed police on the basis of intelligence he was part of a gang and had collected a gun.

Mr Duggan was then shot twice by an officer known as V53, with one shot fatal.

Lawyers representing his mother, Pamela, argued today that article 2 of the European Convention on Human Rights requires "objective" reasons for believing Mr Duggan posed a threat.

Hugh Southey QC, representing the Duggan family, said the inquest had "failed to comply" with article 2 because it only took into consideration "subjective" elements - namely, whether it was V53's honest belief Mr Duggan was carrying a gun.

Last year, Ms Duggan's application for judicial review into whether an inquest jury was entitled to bring in its 8-2 majority "lawful killing" verdict was rejected by three High Court judges.

Mr Duggan's family said they were were "extremely disappointed" with the High Court ruling, but have now been granted leave to appeal the decision by the Court of Appeal. If they win it could result in a new inquest.

Mr Southey explained the original jury had been asked to conclude whether Mr Duggan was lawfully killed based solely on the officer's honest belief the victim had a gun in his hand - even if he was mistaken.

"The jury were not asked whether V53's mistake that Mr Duggan had a gun was reasonable," said Mr Southey.

"V53 was mistaken. Eight of the jurors decided 'we are sure that he did not have a gun in his hand.'

"In those circumstances, the appellant submits that an important question was whether V53's mistaken belief was a reasonable mistake for him to have made."

Mr Southey submitted that the shooting brought into question article 2 of the ECHR, which states that deprivation of life is prohibited except where force is "no more than absolutely necessary."

He explained that the jury had to be "capable of determining whether the fatal force was justified, in accordance with the particular meaning given to 'justified' by article 2.

"The appellant submits it can only be justified if it was founded on an honest belief which is mistaken but is based on good reasons," said Mr Southey.

"This is why it is important to consider whether there was an 'objective justification,' rather than just a subjective reason for Mr Duggan posing a threat."

Mr Southey continued: "An investigation into a death for which the state have been responsible must culminate in an expression of the facts relevant to whether the state complied with the substantive article 2 duties."

"The words 'for good reasons' are significant. It cannot be argued that they are irrelevant and meaningless.

"They plainly show that the question whether force is justified is not answered solely by reference to the officer's honest belief.

"Those clear words require the court to go further than asking whether the use of force was 'based on an honest belief... which turns out to be mistaken.'

"They demonstrate that, if the officer's honest belief was mistaken, force may only be justified if the belief was based on good reasons.

"In summary, the investigation must culminate in 'a determination of whether the force used... was or was not justified in the circumstances.'"

Today, Lord Justice Sales granted leave to appeal the findings, saying the Duggan family had an "arguable case."

He specified that he was not speculating whether the case was "likely to succeed," but on the basis of the arguments presented their case had foundation.

Lord Sales said he considered the questions put to the jury by the coroner were "framed too narrowly."

He said he was convinced by arguments that Article 2 stipulates there should be an "objective element" behind whether an officer was justified to act in self defence.

A further compelling argument for his decision, Lord Sales explained, was that "the shooting dead of a suspect by the police is always a matter for careful scrutiny."