Leading Aircraftman Ronald Maddison died at the base in 1953
Military scientists who carried out nerve gas tests on humans in the 1950s acted unethically, a leading expert told an inquest on Wednesday.
Professor Sir Ian Kennedy said researchers were "acting on the edge of their knowledge" when they exposed volunteers to a lethal chemical agent.
The tests were carried out at Porton Down laboratories, on Salisbury Plain.
Sir Ian was speaking at the inquest into the death of 20-year-old RAF serviceman Ronald Maddison in 1953.
The inquest was reopened earlier this year after a verdict of misadventure was rushed through shortly after the death of Mr Maddison, from Co Durham.
He died after having GB Sarin, a lethal chemical agent, dabbed on his skin.
In 2001, after Mr Maddison's death began being re-investigated, Sir Ian, a world-leading professor of ethics, was commissioned by the Ministry of Defence (MoD) to write a chapter of the Porton Down Historical Survey.
The professor concluded that, even after taking into account the differing ethical climate of the 1950s, scientists had not acted properly.
He explained that volunteers' surface skin fat content was critical in the effect Sarin could have on them - a factor not fully understood at the time.
It was discovered after Mr Maddison's death that his skin fat was "practically absent," the inquest was told.
This was a key factor in his death shortly after undergoing the tests, the professor concluded.
"In my view there were trials that went too far," he said.
"They were beyond the bounds of what was ethically permissible despite the imperatives of the Cold War."
On Tuesday, Dr Paul Rice, currently a researcher at Porton Down, insisted his 1950s predecessors had "acted in reasonably good faith."
He was responding to earlier revelations that Sarin tests continued after Mr Maddison's death, despite a Government ban on them.
The inquest continues.