Washington, DC’s chief medical examiner has ruled a Capitol Police officer died of natural causes following multiple strokes after the attack on the Capitol, a finding that will make it harder for prosecutors to charge anyone with his murder.

The medical examiner’s office said on Monday that 42-year-old officer Brian Sicknick died of multiple strokes the day after he was sprayed with a chemical outside the US Capitol while it was under siege.

Officer Sicknick was one of hundreds of Capitol Police officers who battled supporters of former president Donald Trump on January 6, when they stormed the building in an attempt to stop Congress from formally certifying President Joe Biden’s election victory.

Officer Sicknick was sprayed by rioters with a chemical substance about 2.20pm and collapsed about 10pm.

He died in hospital the following day.

Two men – George Tanios and Julian Khater – face charges they assaulted three police officers, including Officer Sicknick, by spraying them with a chemical irritant.

The city said it described the manner of death as “natural” in cases in which a disease alone causes death. If death was “hastened by an injury” then the manner of death is not deemed natural, it said.

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The findings by the medical examiner mean it will be hard for federal prosecutors to bring homicide charges in connection with Officer Sicknick’s death.

The Washington Post first reported the medical examiner’s ruling.

Citing an interview with medical examiner Francisco Diaz, the newspaper said the autopsy found no evidence that Sicknick suffered from any sort of allergic reaction to the chemical spray he was exposed to, nor was there any evidence of internal or external injuries.

-AAP