David Birnie was the eldest of six children, he was born in 1951. Both of his parents were alcoholics, who spent their money mainly on liquor and had little left over for raising their children. They divorced when he was 10 years old and neither parent wanted custody, so he became a ward of the state. In the 1960s, David was hired at a stable as an apprentice jockey. He was fired after a short time when he approached a female customer wearing nothing but a stocking over his head. As he moved into adolescence, he had already spent time in jail for misdemeanors and felonies. A sex and pornography addict as well as a paraphiliac by adulthood, he had a childless first marriage before his common-law marriage with Catherine.


Catherine was born in 1953. Her mother died before her first birthday and she moved to South Africa with her father. At the age of two she returned to Australia to live with her grandparents and then was sent to live with an aunt and uncle a year later. She was a melancholy sort with few friends. It had even been reported that parents in the neighborhood had forbidden their children to play with her. This cultivated in Catherine a strong need to be loved. She met David Birnie as a child, their families lived next to each other. When she was 15, they began a casual sexual relationship which lasted until her marriage to Donald McLaughlin on her 21st birthday. McLaughlin was the son of the family who had engaged her as a domestic. She had six children with McLaughlin, one of whom died in a car accident as a baby. Shortly after this accident, she abandoned her husband and began living with David. She changed her legal surname to Birnie and became completely dependent on him.


In their late teens, they were engaged in quite a crime spree. In 1969, the two were charged with eleven counts of theft along with breaking and entering. David received 9 months in prison. Catherine was pregnant at the time, so she only got probation. A month later, an additional eight counts of theft were brought before the Supreme Court. David's sentence was increased by an additional three years and Catherine's probation was increased by four years. In July of 1970, David Birnie escaped from prison and reunited with Catherine. Shortly afterward, the couple was arrested again and charged with 53 counts of theft, breaking and entering, trespassing, and illegal operation of a motor vehicle. They had wigs, radios, dynamite, detonators, and fuses, with them when they were apprehended. David was sentenced to two and a half years in prison and this time Catherine had to serve six months of hard time. Her baby was taken by the state.

When released from prison, she was hired as a domestic and fell in love with her employers' son. Their first child was killed after being struck by a car at only 7 months old. Then they had another five children before their marriage began to fall apart. Catherine stopped working around the house and taking care of the family. So she left her husband and children and went back to David.

David required intercourse six times a day to keep him sated. During the time Catherine and David were broken up, David insisted upon intercourse with his brother James, himself a convicted sex offender. James' 21st birthday present from his brother was to sleep with Catherine.

 
 

David Birnie had some interesting sexual habits, the least of which was an excessive collection of brutal pornography. He was also known to use a hypodermic needle to inject localized anesthetics into his penis prior to engaging in intercourse. When the extreme measures he employed to achieve sexual excitement no longer worked, David suggested that it would be invigorating for Catherine to watch him rape someone. She believed him and relented.

Though the couple spent much time discussing murder in 1985, their first crime was not planned. Mary Frances Neilson was murdered after going to purchase tires from David Birnie. Mary was studying psychology at the University of Western Australia and worked part time at a deli. She had been planning her employ at the Community Welfare department as a counselor. Mary had been last seen leaving work for a lecture at the college on October 6, 1986. Six days later, her Galant sedan was found across the street from police headquarters in a parking lot where David Birnie had left it.

Following work that day, Mary had gone to David's workplace, but he asked her to meet him at home later to negotiate a price. Unable to resist the temptation, David forced her into the bedroom at knifepoint and stripped of her clothing. They bound, gagged, and chained her to the bed. Mary was raped repeatedly and, as Catherine looked on she asked her husband questions in the hope of discovering what she could do to excite him.  Later, they took her to Glen Eagles National Park and raped her again. Mary begged for her life while David strangled her with a nylon cord, using a tree branch to gradually tighten the noose around her neck. He and Catherine mutilated Mary's body and buried it in a shallow grave.

This crime gave them encouragement, so they took out an ad in the local newspaper: "URGENT. Looking for a lonely young person. Prefer female 19 to24 years, share single room flat." It is not known if the ad brought any lookers, but the second victim did not find her way to the Birnies through this method.


Two weeks after the abduction of Mary Neilson, 15-year-old Susannah Candy was picked up while hitch-hiking on Sterling Highway. She had been an honors student at Hollywood High School. The couple held her for several days and raped her repeatedly. After David finished raping Susannah, Catherine would get into bed with them, knowing this would stimulate her husband. The Birnies made Susannah write two letters to her parents so they would not worry about her. She was to explain that she was safe and just wanted some time to sort out her problems. When they had finished having intercourse with each other on the last night, David attempted to strangle Susannah without success. He then stuffed her mouth full of sleeping pills and waited for her to fall asleep.

Then David told Catherine she could express her undying love for him by finishing off the murder. Catherine obeyed with enthusiasm, not letting go of the cord until Susannah was dead. When asked about this later, Catherine replied, "Because I wanted to see how strong I was within my inner self. I didn't feel a thing. It was like I expected. I was prepared to follow him to the end of the earth and do anything to see that his desires were satisfied. She was female. Females hurt and destroy males."


Noelene Patterson was on her way home from her job as a bar manager at Nedlands Golf Club who had been acquainted with the Birnies to some degree. The couple had helped to wallpaper the 31-year-old's home on a previous occasion. Noelene was having trouble with her car, and the Birnies came along to help her push it to a service station. Then they forced Noelene into their car at knifepoint and took her back to their home. They had planned to kill her the first night, but David kept putting it off. He raped her for three days before Catherine pointed a knife at her own chest and threatened to use it on herself. She forced David to choose between his favorite victim and his devoted wife. Catherine kicked sand in her face once she was dead and when Catherine took police to Noelene Patterson's grave, she spat on it.

Twenty-one year old computer operator Denise Brown was a social butterfly who spent most of her spare time dancing at clubs. She had just left the Coolbellup hotel and was headed home to the apartment she and her boyfriend shared with another couple when the Birnies abducted her at knifepoint on November 4, 1986. She had been waiting for a bus on Stirling Highway. She was raped for two days and then raped in the car while being taken to a pine plantation, where David stabbed her in the neck while raping her again. The stabbing failed to kill her and she sat up, screaming, while they buried her. David then hit her in the head with an axe. When she sat up again, he turned the axe head around and split her skull open with his final blow. Even Catherine was disturbed by the brutality of this final attack on Denise.


The afternoon after the couple had picked up Denise Brown, a 19 year-old girl was offered a ride by two people she later identified as the Birnies. She had been walking home from the university that day and remarked that there had been a third person in the back seat of the couple's car. She was upset to later discover that the third person in the car was probably Denise Brown, who would still have been alive.

The young woman said that something about the situation made her uneasy. The man was avoiding eye contact the whole time and the woman was downing rum and coke. She said the woman did all the talking. Their latest target had assumed the person in the back seat was probably the couple's daughter, but told the woman that walking was exercise she desperately needed and refused to get into the car. As she walked away, the couple continued to sit in their car a minute or two before pulling a U-turn and entering the pine plantation where they would rape and murder Denise Brown.

 
 

Their intended fifth victim was a 16-year-old girl whose name was never released to the public. She into a grocery store on November 10, 1986, naked and crying. When police got there she told them she had been abducted at knifepoint by a couple who then chained her to a bed in their house. She had been dragged into a car by them while she was walking in the suburbs alone. The woman stood by and watched as the man raped her repeatedly. The couple reportedly spoke about the possibility of injecting cocaine into David's penis to heighten his experience. The next morning, Catherine made the girl call her parents and tell them she had spent the night at a friend's house and was okay. The woman then took her back to the bedroom, but left her unsecured to go answer the door for a cocaine dealer. The girl then took off running out a window. She was able to give authorities the address and phone number of the couple who had kept her captive.

Perhaps this seems unnecessarily sloppy to some of you. Fortunately for this latest victim, the manner of Denise Brown's death had so disturbed Catherine Birnie that she had come to the end of her rope. This is perhaps what prompted her to leave their fifth intended victim alone and unrestrained. She had begun to believe the killing would never end and decided to give this victim a fighting chance. When she did, in fact, manage to escape, Catherine's only thought was to how angry David would be with her and whether or not she would be able to come up with a sufficient excuse to placate him.

With the victim free and police at the front door, Catherine admitted knowing the girl but refused to say more without her husband present. David claimed the girl had willingly come home with them to use some drugs and that all sex had been consensual. The couple was detained and confessed readily to the four other murders.

At trial, David pleaded guilty to four counts of murder and one count of abduction and rape. When asked why he did this so readily, he looked toward the victims' families and said, "It's the least I could do." Catherine's competency test found her sane enough to stand trial where she was sentenced to a life term in prison. After their incarceration, they traded over 2,600 letters between each other in their first four years apart, as it was their only form of contact.

On October 5, 2005, David Birnie was found hanged in his cell. Catherine continues to serve her sentence with little hope of gaining parole.