In prison awaiting sentence for murdering his wife, Des Campbell has been given two weeks to show good cause as to why he should not be dismissed from the NSW Ambulance Service.The ambulance officer was suspended on full pay when he was charged last September with the murder of his wife, Janet.On Tuesday he was convicted by a Supreme Court jury, which found he pushed Mrs Campbell over a cliff in the Royal National Park in 2005.Campbell, 52, is being held at Silverwater's Metropolitan Remand and Reception Centre and yesterday was served with papers informing him his pay had been suspended. He has until June 1 to argue why he should not be sacked.The move came as Opposition health spokeswoman Jillian Skinner called for an explanation into how he was employed by the ambulance service when he had a previous conviction.Campbell's criminal record in Victoria includes a suspended two-month jail term for assault in 1994. An ambulance service spokesman said background checks with all state police forces and the federal police were now conducted on prospective employees, but the checks were only state-wide at the time Campbell joined in 1999.Campbell left the army and police forces in Victoria and Surrey, England, after disciplinary investigations against him. He quit the Surrey Police before a disciplinary hearing, after a woman accused him of assault. No charges were laid. Campbell will face court again in July.