Matthew James Harris was born on June 30, 1968, in New South Wales, Australia, and grew up in the regional city of Wagga Wagga. Much of his early life remains private in official records, but later psychiatric reports referenced deep‑rooted emotional distress that Harris linked to being adopted, a grievance he frequently mentioned during interviews with police. His statements suggested years of simmering resentment, social detachment, and a long‑standing struggle with self‑worth.

People who knew Harris in adulthood described him as an isolated figure who walked long distances around Wagga Wagga, often drinking heavily. He lacked stable employment and appeared to drift through life without meaningful relationships or long-term goals. By the late 1990s, Harris had developed daily alcohol habits, used heroin, and exhibited increasing anger, resentment, and emotional volatility.

When psychiatrists later evaluated him, they diagnosed avoidant, schizoid, and schizotypal personality disorders, conditions that contributed to his chronic social withdrawal, flattened emotional response, and distorted thought patterns. He displayed a blunt, detached manner when discussing violence and frequently framed his actions as expressions of anger toward the world rather than towards the individual victims.

Harris’ life began spiraling sharply in 1998. He spent much of that year drinking, wandering Wagga Wagga’s streets, and expressing resentment over perceived slights and longstanding emotional wounds. His crimes unfolded suddenly, intensely, and within a short period, marking an alarming escalation from petty criminal behaviors to murder.

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.