THE Ministry of Defence can challenge an inquest verdict on the death of a young airman who was deliberately exposed to a deadly nerve agent half a century ago, a High Court judge has ruled.

A coroner's jury returned a verdict of unlawful killing on the death half a century ago of Ronald Maddison of Consett.

The judge, Mr Justice Collins, said he was giving no view on whether the MoD's challenge would eventually succeed, but expressed the opinion that the Ministry's case was 'arguable' and should proceed to a full High Court hearing.

The family of Ronald Maddison have until May 20 to put their case in writing and the judge left the door open for them to argue that the MoD's bid to overturn the verdict should be stopped in its tracks.

Mr Maddison died after having drops of the nerve agent Sarin dabbed on his arm at the Porton Down chemical warfare testing facility in Wiltshire in 1953, when he was 20 years old.

His family claim he and other military personnel were tricked into taking part in what they believed were harmless experiments.

In November last year, inquest jurors sitting in Trowbridge returned an unlawful killing verdict after a 64-day hearing before the Wiltshire coroner, David Masters. The jurors rejected the MoD's plea that all the servicemen who were tested at Porton Down were told beforehand that they were taking part in nerve gas experiments.

However, the MoD's legal team say the jury's verdict should be overturned.

They argue there was not enough evidence for the jury to find beyond reasonable doubt that Mr Maddison did not consent to the testing.

However, Nick Brown, representing Mr Maddison's sister, Lilias Craik, and other members of his family, was given until May 20 to put in full written arguments in support of the jury's verdict.

The final decision on whether the MoD's challenge can proceed to a full hearing will be made by a High Court judge on consideration of written arguments from all sides.

The family's legal team was not available for comment.