McClinton joined the UDA after leaving the UDR and, with his military background, was soon added to the ranks of their
Ulster Freedom Fighters (UFF), its branch responsible for committing violent attacks. He became commander of several UFF
active service units and through these was involved in a series of what he later admitted were particularly brutal attacks. McClinton has refused to reveal any details of these events, despite admitting his involvement in this type of activity, as he has never been charged for them. After becoming a committed
born-again Christian in the
H Blocks, McClinton, led by his faith, wrote sixteen statements of full responsibility for very serious UFF terrorist offences, got the
RUC/C.I.D. officers to the
Maze Prison, and gave them the signed statements of guilt. These charges were sent to the
Director of Public Prosecution with recommendations from Tennent Street RUC that there be 'no prosecution', since McClinton was already serving life sentences. This recommendation was accepted by the DPP. McClinton was ultimately charged with two murders. In March 1977 McClinton murdered Catholic civilian Daniel Carville. The attack took place as Carville was driving his son down Cambrai Street, which links the Shankill and
Crumlin Roads, on St Patrick's Day. McClinton admitted in later life that at this time he wished to behead IRA terrorists and place the severed heads on the railings of the Shankill's Woodvale Park, in order to 'terrorise the terrorists', as was UFF policy.
Jim Craig, however, began to fear that McClinton, with his extreme suggestions about murder, was becoming too dangerous and a possible rival to him as leader of C Company UFF . Therefore, he contacted members of the police he knew to give McClinton up to them. ==Arrest and imprisonment==