David and Catherine Birnie

David Birnie was the oldest of five children and grew up in Wattle Grove, a semi-rural suburb of Perth. School friends and church acquaintances remember Birnie's family as having been dysfunctional, and subject to frequent rumors involving alcoholism, promiscuity, and incest. The family never had regular meals together, and Birnie's parents did not cook meals for their children.

In the early 1960s, Birnie's parents decided to move the family to another Perth suburb, where he eventually met Catherine Harrison through mutual friends. At age 15, he left school to become an apprentice jockey for Eric Parnham at the nearby Ascot Racecourse. During his time there, Birnie physically abused the horses and developed a habit of exhibitionism. One night, Birnie, wearing only stockings over his head, broke into the room of an elderly lady where he was boarding and attempted to rape her.

By the time he was an adolescent, Birnie had been in and out of prison for several misdemeanors and felonies. As an adult, he became addicted to sex and pornography, and was a paraphiliac. In his early 20s he married his first wife and had a daughter, Tanya, who was aged 10 at the time of his arrest. Tanya, who has changed her surname since Birnie's capture, has never married and had no children, stating, "I don't wanna spawn another David Birnie".[2]

In late 1986, at the time of the murders, Birnie was employed at a car wrecker's shop in Willagee, a suburb of Perth.

Catherine Birnie was born Catherine Margaret Harrison on 23 May 1951. She was two years old when her mother, Doreen, died giving birth to her brother, who himself died two days later. Unable to raise Catherine, her father Harold sent the girl to live with her maternal grandparents. When she was aged 10, a custody dispute resulted in Harold regaining sole custody of Catherine.

Catherine met David at age 12 and began a relationship with him two years later. Her father pleaded with her on several occasions to leave David due to the fact that her involvement with him led to her getting into trouble with local police, resulting in her being sent to a youth prison in adolescence. This offered Catherine a chance to break away from David. Encouraged by a parole officer, she began working for the McLaughlin family as a housekeeper. She married Donald McLaughlin on her 21st birthday and had seven children; their firstborn, a son, was struck and killed by a car in infancy.

In 1985, Catherine left her family and went to live with David.[3] The couple were never legally married, but Catherine changed her surname by deed poll to Birnie.[4]

Over a period of five weeks,[5] the Birnies abducted five women, aged between 15 and 31. All of the victims, except for one, were raped and murdered. The sole exception was their final victim, who escaped the day after her abduction and led police back to the Birnie house, thus ending their crime spree.

When sent to trial, David pleaded guilty to four counts of murder and one count each of abduction and rape. When asked why he had pleaded guilty, he gestured toward the victims' families and said, "It's the least I could do." He was sentenced to four terms of life imprisonment. After being found sane enough to stand trial, Catherine was also sentenced to four terms of life imprisonment by the Supreme Court of Western Australia; under law at the time, both were required to serve 20 years before being eligible for parole.

Initially, David was held at the maximum-security Fremantle Prison, but he was soon moved to solitary confinement to keep him from coming to harm from other prisoners. Three of the original death row cells were converted for him and he stayed there until the prison was closed in 1991. The cell can occasionally be viewed on the True Crime Tour held daily at Fremantle Prison. While incarcerated, the Birnies exchanged more than 2,600 letters but were not allowed any other form of contact.[18]

David was found dead in his cell at Casuarina Prison on 7 October 2005 at 4:30am (WST).[19] He was 54 years old. An inquest found that he had hanged himself from an air vent using a length of cord.[5] Various factors led to his suicide; a failure to provide him with his antidepressants had exacerbated his depression, his computer had been confiscated and he was suspected of sexually assaulting another prisoner.[5] He was described by a former prison officer as a 'model prisoner' who looked after injured animals.[20] Catherine was not allowed to attend his funeral.[21]

Catherine is imprisoned in Bandyup Women's Prison. Since being incarcerated she has worked as a prison librarian and appeared in a prison production of Nunsense.[22] In 2007, her parole application was rejected and the then Attorney-General of Western Australia, Jim McGinty, said that her release was unlikely while he remained in office.[23]

Catherine's case was to be reviewed again in January 2010; however, on 14 March 2009, new Western Australian Attorney-General Christian Porter, following requests from the victims' families, determined she would stay in jail for life. This decision makes her the third Australian woman (after Katherine Knight and Patricia Byers) to have her papers marked "never to be released".[24] Her appeal of this decision was turned down in March 2010 by Porter.[25] Her fourth bid for parole was declined in 2016.[26] That same year, Kate Moir began a campaign to end Western Australian laws that automatically put convicts up for parole every three years.[27] Moir has stated Birnie has never even applied for parole.[28]

In 2017, Catherine's youngest son, under the alias Peter, called for her execution, stating that his relation to her has resulted in him being assaulted on multiple occasions.[22] He also supports Moir's campaign.[29][30]

The case was included in Season 1, Episode 6 ("The Moorhouse Horrors") of Crime Investigation Australia, first aired 2005.

The case formed an episode of Australian Families of Crime. Nine Network Australia (2010).

The case was covered by Casefile True Crime Podcast on 27 August 2016.

On 9 November 2017, the case was discussed by Georgia Hardstark in an episode of the podcast My Favorite Murder.

The case was detailed on episode 75 of the True Crime All the Time podcast on 22 April 2018.

The 2016 Australian film Hounds of Love is based on several true murders, but most closely resembles the Moorhouse Murders.

Both Catherine and David Birnie were also featured on Deadly Women in the 8th episode from Season 3 called "Fatal Obsession."

The case was covered by Morbid: A True Crime Podcast on May 8, 2021, as a part of a two-episode series, titled "Episode 230: Catherine & David Birnie Part 1" and "Episode 231: Catherine & David Birnie Part 2" The case was also covered by The Serialholic podcast on July 3, 2019, titled "David & Catherine Birnie"

• List of serial killers by country

• "Case 31: The Killer Couple". Casefile True Crime Podcast. 27 August 2016.
• Snyder, M. "Catherine Birnie – Australia". Female Serial Killers. Archived from the original on 15 July 2004.