Seamus Kearney's lawyers argued that the judge in the non-jury trial mistakenly accepted uncorroborated evidence that the stubs were clean and fresh when retrieved.Kearney, 57, of Gorteade Road, Maghera, Co Londonderry, was sentenced to at least 20 years in jail last month for the murder of John Proctor.Mr Proctor, a 25-year-old RUC Reserve Constable, was shot dead by the IRA minutes after visiting his wife and newborn son at the Mid Ulster Hospital, Magherafelt in September 1981.Kearney had denied murder and possessing an Armalite AR15 rifle.But a judge found him guilty after hearing key evidence that his DNA profile was on a cigarette butt found among spent bullet casings at the scene.He was held to be either the gunman, the driver of a Ford Escort RS200 used by the killers, or an occupant of the car present to provide support.Even though Kearney is expected to serve only two years of his jail term under the terms of the Good Friday Agreement, he mounted a challenge to both the conviction and sentence.The prosecution argued that his refusal to enter the witness box at trial strengthened its case that he had no innocent explanation for the DNA match.But on Thursday defence counsel Arthur Harvey QC questioned the evidence said to show the two retrieved cigarette ends were discarded at the time of the shooting, rather than some significant period beforehand.The barrister contended that the condition of the butts, given by a police constable who picked them up, was accepted without any notes to back up his assertion."The trial judge starts off with a premise that these cigarette butts were clean and dry," Mr Harvey told the Court of Appeal."Therefore there is a knock-on proposition from that."According to Mr Harvey the passage of time meant it was difficult, if not impossible, to assess the gathering of evidence back in 1981.He added: "Once you come to the conclusion that they were very fresh and very clean then that leads to other conclusions which, I submit, the learned trial judge fell into error on."Following submissions the three appeal judges, Lord Justice Girvan, Lord Justice Coghlin and Mr Justice Weatherup, reserved their verdict.