Marion Watt (45), Vivienne Watt (16) and Margaret Brown (41): Marion, her daughter Vivienne, and her sister Margaret were shot dead in their home in Burnside, Lanarkshire on 17 September 1956. At the time of the murders, Manuel was out on bail for housebreaking at a nearby colliery and officers in charge of the manhunt for the Watts' killer suspected him. However, for a time the main suspect was Marion's husband, William, who had been on a fishing holiday in Ardrishaig, but was suspected of driving around 90 miles through the night, faking a break-in to his own house, murdering his family, and driving back. The ferryman on the Renfrew Ferry claimed to have seen him on the ferry during the night (although this was not the most direct route) and a motorist claimed to have passed him on Loch Lomondside. Both witnesses picked him out at an identity parade. William Watt was arrested and held on remand in Barlinnie Prison, then released two months later, after the police realised that they could not make the case against him stick, and the ferryman seemed confused about what type of car he had driven. The police did not find any serious motive which might have led Watt to murder his family, although it emerged that he had a number of affairs during his marriage. Police frogmen searched the Crinan Canal next to the hotel where Watt had stayed, looking for a murder weapon and bloodstained clothing, but the weapon was in another stretch of water further south. It was established that the level of petrol in Watt's car had not fallen during his alleged overnight drive, so the police questioned petrol stations along the route to see if he had refuelled, and even speculated that he might have had a secret cache of petrol, and searched the route for it. William Watt remained the main suspect until the Smart family murder just a few miles away, when the police realised that there was a serial killer on the loose. At Manuel's trial, the defence argued that Watt had committed these murders.