Matthew James Harris was born on June 30, 1968, in Wagga Wagga, New South Wales, Australia.

On June 20, 1998, Matthew James Harris, along with Kenneth Scott Frazier, committed a robbery at the home of Trang Nguyen. They entered her house and threatened her with a knife. Nguyen was at home with her three children. The men stole $58 from her, which they later spent on alcohol.

Harris killed Peter Wennerbom on October 1, 1998. Wennerbom was 62 years old and was the brother of one of Harris's friends. Harris forced his way into Wennerbom's home and strangled him to death. Later, he told police that Wennerbom offered no resistance and that he felt in total control during the crime.

On October 17, 1998, Harris visited Yvonne Ford, a 33-year-old woman with a mild intellectual handicap. He admitted that he felt a "friendship" with her but later developed violent thoughts. While they were in the bath, Harris strangled Ford and held her under water for 3 to 4 minutes. He later expressed that he felt powerful and angry after the murder.

On November 3, 1998, Harris killed his neighbor, Ronald Galvin. He strangled Galvin, and the next day, he borrowed a car to transport Galvin's body to Uranquinty. Harris described this murder as a way to release his anger.

Harris attempted suicide twice with heroin shortly after the murder of Galvin and again on December 1, 1998, the day he was arrested.

On December 3, 1999, Harris pleaded guilty to the murders of Wennerbom, Ford, and Galvin, as well as to the robbery of Trang Nguyen. He was sentenced to three concurrent 40-year terms for the murders and three additional years for the robbery. He became eligible for parole in 2023. However, on December 20, 2000, an appeal changed his sentence to life imprisonment without parole for the murders. The court decided that Harris was too dangerous to be released.