Stephen Silver appeals conviction for murder of Detective Garda Colm Horkan

The motorbike mechanic claims psychiatric evidence contradicted legal test for insanity

Stephen Silver (pictured) a motorbike mechanic from Aughaward, Foxford, Co Mayo, had pleaded not guilty to the murder of Det. Gda Horkan knowing or being reckless as to whether he was a member of An Garda Siochana acting in the course of his duty. File picture: Michael McCormack/PA

Stephen Silver, who shot and murdered Garda Colm Horkan after taking the garda's own gun from its holster, has appealed his conviction claiming that the State's psychiatric evidence contradicted the legal test for insanity.

Silver's lawyers had argued at his trial that his responsibility for the killing was substantially diminished by his mental illness and that he therefore qualified for a manslaughter verdict under the Criminal Law (Insanity) Act 2006.