Ronald Maddison, from Consett, County Durham, died after having drops of Sarin dabbed on his arm at Porton Down chemical warfare testing facility in Wiltshire in 1953.
His family claim he and other military personnel were duped into taking part in what they believed were harmless experiments. It took jurors sitting in Trowbridge five hours to reach their verdict on the 64th day of the inquest.
Mr Maddison, a Leading Aircraftman based in Swindon, was one of many human volunteers involved in tests from 1939 to 1989 and lawyers believe the verdict could open the door for other service personnel to sue the Ministry of Defence.
The inquest was the second to be held into Mr Maddison’s death. Lord Chief Justice Lord Woolf quashed the original verdict of death by misadventure in 2002 and said a new inquest was needed in the interests of justice.
The jury of six men and four women concluded yesterday that the cause of Mr Maddison’s death was “application of a nerve agent in a non-therapeutic experiment”.
A spokesman for the MoD said: “the Ministry of Defence notes the jury’s findings and will now take some time to reflect on these”.
The new inquest was ordered after Coroner David Masters was given files by Wiltshire police documenting the “insufficiency of the original inquest and that the coroner in 1953 was not apparently provided with all the relevant material”.