A British coroner is investigating the death of airman Ronald Maddison, who died in May, 1953 after scientists at the military's Porton Down laboratory placed a patch of liquid nerve agent on his arm in an experiment.
The original inquest 50 years ago ruled that his death was an accident. But it was reopened this year after pressure from Maddison's family and campaigners for more than 3,000 other servicemen used as guinea pigs in chemical weapons tests.
Campaigners say the case could lead to criminal charges against officials involved in the tests.
The hearings heard that on the day after Maddison's death, the government ordered a halt to nerve agent tests on troops.
"Pending the results of our own court of inquiry, I have given instructions that further tests on human beings with nerve gas should be temporarily suspended," Duncan Sandys, the minister responsible for Porton Down, wrote in a secret memo to then-prime minister Winston Churchill.
But other records read out by the coroner showed that scientists built a "mobile chamber" and exposed groups of servicemen to Sarin nerve gas in it on three separate occasions in July and August, 1953, while the ban was in force.
The texts of the documents were reported in the Guardian newspaper. A government source confirmed the paper's account.
But a spokesman for the Ministry of Defence declined comment pending the outcome of the hearings.