Peter Britton Tobin was born on August 27, 1946, in Johnstone, Renfrewshire, Scotland. He was the youngest of eight children in his family, with four older sisters and three older brothers. His father was Daniel Tobin, and his mother was Marjorie, also known as Margaret. Peter was known to be a difficult child, which led to problems in his early life.

At the age of seven, in 1953, Peter was sent to an approved school because of his behavior. He later reported that he joined the French Foreign Legion but eventually deserted. Following this, he spent time in a borstal, which is a type of youth detention center. In 1970, he was convicted of burglary and forgery in England, which resulted in a prison sentence.

In 1969, Tobin moved to Brighton, Sussex, where he married his 17-year-old girlfriend, Margaret Mountney. The marriage did not last long, and the couple separated after only one year. Margaret divorced Tobin in 1971.

In 1973, Tobin married Sylvia Jefferies, a nurse who was 30 years old at the time. They had a son named Ian later that same year. They also had a daughter named Claire in 1975, but she unfortunately died shortly after birth. Their marriage lasted until 

1976 when Sylvia left Tobin and took their son with her.

After his second marriage, he had a relationship with Cathy Wilson. They married in 1989 when Tobin was about 43 years old. The couple had a son named Daniel later that year. In 1990, they moved to Bathgate, West Lothian, Scotland. However, Cathy left Tobin in the same year and returned to Portsmouth.

Throughout his adult life, Tobin's relationships seemed to follow a pattern. His wives later described him as a charming man who could turn violent and had a sadistic side. By May 1991, he moved to Margate, Kent, and later to Havant, Hampshire to be closer to his younger son.

On August 4, 1993, Peter Tobin attacked two 14-year-old girls at his flat in Leigh Park, Havant. They had come to visit a neighbor who was not home and stopped at Tobin's flat to wait. Tobin held them at knife-point and forced them to drink alcohol. He sexually assaulted and raped both girls. During the attack, he stabbed one of them while his younger son was present. After the assault, he attempted to leave the girls for dead by turning on the gas cooker without lighting it. Fortunately, both girls survived. Tobin went into hiding afterward, assuming a false identity while hiding with a religious group. He was captured in Brighton in 1994 and sentenced to fourteen years in prison.

In September 2006, while working as a church handyman in Glasgow, Tobin killed 23-year-old Angelika Kluk. He was known as "Pat McLaughlin" at the time and had been avoiding the police. Kluk was last seen alive in his company on September 24, 2006. Tobin assaulted, raped, and stabbed her, then concealed her body beneath the floorboards of St. Patrick's Church. Her body was discovered on September 29. Tobin was arrested shortly after and found guilty of her murder in May 2007, receiving a life sentence.

In the following years, police investigations connected Tobin to the disappearances of two young women, Vicky Hamilton and Dinah McNicol, who went missing in 1991. Vicky was last seen on February 10, 1991, near a bus stop in Bathgate and was later found buried in Tobin's Margate garden in November 2007. Dinah was last seen hitchhiking home on August 5, 1991, and her remains were also discovered at the same location. On December 2, 2008, Tobin was convicted of Hamilton's murder, and on December 16, 2009, he was found guilty of McNicol’s murder. Each conviction resulted in additional life sentences.

Tobin's case led to a significant investigation called Operation Anagram. This investigation looked into other unsolved murders and missing person cases across the UK, as Tobin had lived in several locations. Despite claiming to have forty-eight victims, no other murders were conclusively linked to him. He was diagnosed as a psychopath while in prison. Tobin died on October 8, 2022, at the age of 76.