The Guardian has been found to be in breach of the Press Complaints Commission code of practice over a headline and subhead on an article published by the newspaper in November regarding the circumstances of the death of Mark Duggan, whose shooting by the police prompted the summer riots.

However, the PCC also ruled that the combination of steps taken by the Guardian to remedy the error met the requirement of the editors' code. The complaint was therefore not upheld because the mistake had already been corrected.

The PCC concluded that the article's original headline "Revealed: man whose shooting triggered riots was not armed" was in breach of the editors' code provision on accuracy, following complaints from the Metropolitan police and the Independent Police Complaints Commission, which had been investigating Duggan's death.

Both the Met and the IPCC said that the headline and a related subhead were misleading, because it was wrong to infer that Duggan was unarmed because he was not found carrying a gun when he was shot dead by police on 4 August 2011. In fact, a gun collected by the deceased was found nearby.

The complaints did not focus on the body text of the article, published in print on 19 November, which said: "A gun collected by Duggan earlier in the day was recovered 10 to 14 feet away, on the other side of a low fence from his body. He was killed outside the vehicle he was travelling in, after a police marksman fired twice."

Following an investigation into the complaints, the PCC ruled that the Guardian had failed to take care not to publish inaccurate or misleading information in breach of clause 1 of the editors' code of practice, which deals with accuracy. The body took the view that the error was "significant and avoidable" – and noted the "over-riding" responsibility that newspapers have to take care over the presentation of stories at particularly sensitive times.

Following direct representations from the IPCC to the newspaper at the time, the Guardian initially amended the subhead in later print editions to say that there was "no forensic evidence" that Duggan had been carrying a gun when he was shot. However, the police watchdog was not satisfied with this, and made public statements of concern along with the Met.

At about 6.30pm the headline to the article online was changed to "New questions raised over Duggan shooting", 21 hours after the IPCC first raised its concerns. The newspaper subsequently corrected the story in its corrections and clarifications column and apologised for the errors.

A week later, the Guardian published a column by its readers' editor, whose own investigation concluded that the newspaper had taken "too long" to respond to the IPCC's concerns, and that there had been "serious failings" in its editorial processes.

Stephen Abell, the director of the PCC, said: "This was an important story about a man whose death had significant societal and political implications. The requirement for editors to 'take care not to publish inaccurate, misleading or distorted information' is at the heart of the editors' code, and it was absolutely right for the newspaper to take the steps it did to properly remedy the situation once the error had been recognised."

Clause 1 of the editors' code, which deals with accuracy, reads as follows: "i) The press must take care not to publish inaccurate, misleading or distorted information, including pictures.

"ii) A significant inaccuracy, misleading statement or distortion once recognised must be corrected, promptly and with due prominence, and – where appropriate – an apology published. In cases involving the commission, prominence should be agreed with the PCC in advance."

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