But William Watt was innocent.
Not only did he lose his wife Marion, daughter Vivienne and sister-in-law Margaret Brown – shot in the head by Manuel – he found himself in Barlinnie suspected of the murders himself.
Ironically, Manuel had been put in a Barlinnie cell not too far away, accused of housebreaking.
When Manuel was on a bloody rampage in the Watts’ Burnside bungalow in September 1956, the head of the house was taking a fishing holiday break in Argyll from his bakery business.
The Watts and Mrs Brown died at 6am. William had breakfast at 8am in Lochgilphead.
Police believed he had returned to the outskirts of Glasgow to kill his family and then driven back to Argyll to establish an alibi.
Even Formula 1’s finest would find that impossible in a frost-covered ’50s saloon, especially if the long road journey included a river crossing by ferry.
The police took seriously unreliable reports that he had been seen driving around Loch Lomondside that night and that he had been on the Renfrew Ferry.
It led to a bereaved father and husband spending 67 tortured days in Barlinnie.
Watt’s release was secured when he was taken on by legal ace Laurence Dowdall.
Manuel, a suspect in both the Watt and Anne Kneillands cases, met Dowdall and let slip that Mrs Brown had been shot twice. When he checked, police confirmed it but they refused to arrest Manuel.
That misjudgment led to the deaths of five more people before Manuel faced a jury.