Peter Demeter was born on April 19, 1933, in Budapest, Hungary. He came from a wealthy family, but everything changed after World War II. The rise of the Communist government led to his family's fortune being lost. This hardship affected many families in Hungary during that time.

In 1956, when Peter was 23 years old, he decided to leave Hungary. He was among about 200,000 refugees who fled the country during the Hungarian Revolution. Soviet forces had suppressed the revolution, and many people, including Demeter, wanted to escape the oppressive circumstances of their homeland. He emigrated to Canada and began to build a new life.

By 1962, Peter Demeter had started a career as a land developer in Toronto. He found success in this field and began to establish himself in his new country.

In 1967, Peter married Christine Ferrari, who was an Austrian-born model. They had a daughter named Andrea together. However, their marriage faced difficulties over time and became strained.

Peter Demeter was charged with the murder of his wife, Christine, on July 18, 1973, at their home in Mississauga, Ontario. The trial took place in London, Ontario, and involved lawyers Edward Greenspan and Joseph Pomerant. This trial became known as the longest in Canadian history at that time. On December 6, 1974, Demeter was convicted of arranging for Christine's murder and received a life sentence.

The prosecution relied on two key witnesses. One was a man known as Mr. X, who wore a hood during the trial to protect his identity. He was later revealed to be Gyala Virag, who testified that Demeter hired a contract killer named "The Duck," identified as Imre Olejnyik. The other major witness was Csaba Szilagy, a former friend of Demeter, who claimed that Demeter had also tried to hire him to kill someone named Ferrari. The prosecution's case was further supported by secret recordings of conversations between Szilagy and Demeter after Christine's death.

During the trial, it came to light that both Peter and Christine may have been plotting to kill each other to obtain a $1 million life insurance policy. Demeter did not testify in his defense and continued to assert his innocence. Following the conviction, the Canadian government sought the extradition of Imre Olejnyik from Hungary, but he was never located. Reports later indicated that Olejnyik died in Hungary in 1975.

In 1983, while residing at a halfway house, Demeter faced new charges for conspiring to kidnap and murder the son of his cousin, who was managing Demeter's financial affairs. He planned this to gain money. In July 1985, Demeter was convicted of these charges and received a second life sentence. He was also charged with arson related to his family home in Mississauga. In 1988, he faced additional charges for attempting to kidnap and murder the daughter of his lawyer, adding two more life sentences to his record.

In May 2006, a judge ordered Demeter to submit a DNA sample for the national DNA database, which he refused. Throughout his time in prison, he has had health issues, including a stroke, a heart attack, and several cancer diagnoses, for which he received chemotherapy. As of now, he is serving his sentences at a medium-security prison in Bath, Ontario. In March 2019, he applied for parole after more than 20 years but was denied release.