Peter Manuel was born to Scottish parents in New York City; the family moved to Detroit, Michigan before migrating back to Scotland in 1932, this time to Birkenshaw, Lanarkshire.

On 2 January 1956, Manuel stalked Kneilands at the (now removed) East Kilbride golf course in the Calderwood area,[1] raped, and bludgeoned her to death with a length of iron.

Manuel shot Marion, her daughter Vivienne, and her sister Margaret 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.

William Watt was arrested and held on remand in Barlinnie Prison, then released two months later after the police realized 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.

William Watt remained the main suspect until the Smart family murder just a few miles away when the police realized that there was a serial killer on the loose.

Manuel definitely did attend a job interview in Newcastle two days before this murder, but it is not clear that he hung around in the area; he could have just gone home to Scotland.

After the murders, Manuel stayed in their house for nearly a week, eating leftovers from their Hogmanay meal and even feeding the family cat.

Although many police officers who were familiar with Manuel suspected him of carrying out these murders, they were unable to prove his guilt until shortly after they had searched the Smarts' residence.

After the police arrested his father, Peter Manuel confessed to eight of these murders (but not that of Dunn) and provided incriminating information only the perpetrator could have known.

Although the judge, Lord Cameron, admitted that Manuel conducted his defence "with a skill that is quite remarkable," the killer was unable to convince the jury of his innocence and was found guilty of all charges against him, except for that of murdering Anne Kneilands, which had been dropped due to lack of evidence.

Anthony Miller followed Manuel on to the Barlinnie gallows in December 1960, and Henry John Burnett was executed at Craiginches Prison, Aberdeen, in August 1963.

[10] Manuel had been arrested only eight days after the City of Glasgow CID took over the case, leading to calls for the creation of a national police force.