A High Court judge is due to rule whether a former aide to Colonel Muammar Gaddafi can be held jointly liable for the fatal shooting of Pc Yvonne Fletcher 37 years ago.

Pc Fletcher, 25, was killed while policing a demonstration against the former Libyan leader outside his country’s embassy in St James’s Square in central London on April 17 1984.

Retired police officer John Murray, 66, has brought a civil claim for a nominal amount of £1 against Saleh Ibrahim Mabrouk as part of his decades-long attempt to find “justice” for his dead friend.

Lawyers for Mr Murray have accused Mr Mabrouk, who has denied any wrongdoing, of being “jointly liable” for the shooting, arguing that, while he did not fire any shots, he was “instrumental” in the “orchestration” of a plan to use violence at the protest.

A three-day trial at the Royal Courts of Justice in London heard that Mr Murray, who has suffered post-traumatic stress disorder (PTSD) since the incident, was seeking “vindicatory” damages for alleged assault and battery.

The court heard that Mr Murray, from Chingford, east London, promised his dying colleague he would find those responsible for the shots that were fired from an embassy window.

Mr Mabrouk was arrested in 2015 in connection with Pc Fletcher’s death, but two years later the Metropolitan Police said charges could not be brought because key evidence had been kept secret to protect national security.

He has not taken part in court proceedings but previously denied any involvement in Pc Fletcher’s death, highlighting that he had been arrested earlier, before the shots were fired.

Mr Justice Martin Spencer is expected to deliver his judgment at the Royal Courts of Justice on Tuesday morning.