Peter Thomas Anthony Manuel was born on March 13, 1927, in New York City to Scottish parents. When he was just a child, his family moved to Detroit, Michigan. In 1932, they relocated back to Scotland, settling in Birkenshaw, Lanarkshire. Manuel's early life was marked by challenges. He experienced bullying during his childhood, which likely affected him deeply.

By the age of ten, Manuel began to encounter trouble with the law. He became known to local police as a petty thief, engaging in small crimes. As he grew older, his behavior escalated. At 16, he committed a string of sexual assaults. This led to a sentence of nine years at Peterhead Prison.

After serving time, Manuel returned to society but did not change his ways. In 1955, he faced another legal issue. He represented himself at Airdrie Sheriff Court in a rape case and successfully defended himself against the charges. 

Peter Manuel committed a series of murders in Scotland between 1956 and 1958. His first known victim was Anne Kneilands, a 17-year-old girl. She was murdered on January 2, 1956, after leaving a friend's house. Manuel stalked her and brutally killed her with a metal object. Although he later confessed, he was never charged for this murder due to lack of evidence.

Manuel later killed Marion Watt, her 16-year-old daughter Vivienne, and Vivienne's aunt, Margaret Brown, on September 17, 1956. They were shot in their home in Burnside, Glasgow. At the time of these murders, Manuel was out on bail for a burglary. There was initial suspicion around Marion's husband, William Watt, but he was eventually cleared.

On December 8, 1957, Manuel is believed to have killed Sydney Dunn, a taxi driver in Newcastle. Dunn's body was found on moorlands soon after, with evidence pointing to Manuel, but he was never charged for this crime.

Isabelle Cooke, another of Manuel's victims, disappeared on December 28, 1957. She was last seen leaving home for a dance at her school. Manuel stalked her, raped her, and strangled her. He later led police to her body, which he had buried in a field.

The last of Manuel's confirmed murders were Peter Smart, his wife Doris, and their 10-year-old son Michael. They were shot in their Uddingston home on January 1, 1958. After the murders, Manuel stayed in their house for several days, living off the family's food and using their car before abandoning it.

Manuel was arrested on January 14, 1958, after police connected him to the Smart family murders through the use of stolen banknotes. During interrogation, he confessed to multiple murders, including those of the Watt family and Isabelle Cooke, but not to Sydney Dunn's murder.

Manuel's trial took place in May 1958, where he represented himself and tried to defend his actions but was found guilty of seven murders. He was sentenced to death and was executed by hanging on July 11, 1958, at Barlinnie Prison.