In June 2009 Patrick Maqubela's body was found in his bed in his Bantry Bay flat. The acting judge had been dead for two days when he was discovered shrouded in a sheet with the heater on and the curtains drawn. He is thought to have been suffocated with clingwrap.
His wife, Thandi Maqubela, is in jail for his murder.
A forged will, and phone calls to his life insurer shortly before his death, pointed to a motive of money. Judge John Murphy's judgment at her trial resonates with the latest research on women killers across the globe: "The evidence shows beyond all doubt her proclivity towards deception, fraudulent conduct, and an almost delusional tendency to fabricate, aimed unrealistically at self-preservation and advancement."
Maqubela had hired hitmen to help her carry out the deed.
A growing interest over the past five years in women who commit murder has produced some uncomfortable theories on how we have evolved across gender lines: men kill for sex, women kill for money.
Marissa Harrison, an evolutionary psychologist at Pennsylvania State University, argues that women, with their finite supply of eggs, have "limited reproductive potential" and have thus "evolved to place a premium on securing resources". Men, with their "relatively unlimited sperm", are likely "predisposed to seek a vast number of sexual opportunities".
Harrison led one of the biggest studies on female killers to date: her research, which focused on women who had killed three people or more with a "cooling-off period" of at least a week between murders, looked at 64 such killers in the US who committed their crimes between 1821 and 2008.
This took her into the heart of some notorious cases which are as intriguing today as they were when they happened.
Jane Toppan, a nurse at Cambridge Hospital in Massachusetts, administered deadly morphine cocktails and other poisons to more than 30 people. In 1901 she confessed to the murders.
While most of her victims were patients in her care, they also included her best childhood friend and her foster sister.
Dorothea Puente, dubbed the Death House Landlady, ran a boarding house for the elderly and infirm in California in the 1980s. She would cash in her tenants' security cheques, and kill them off in cold blood if they moaned about it.
Police discovered seven bodies buried in her backyard.
While there were variations, the killers explored by Harrison and her team typically had a caregiving role (nurses, stay-at-home moms, Sunday school teachers, babysitters), were well-educated, and were white.
Her findings relate directly to evolutionary psychology — how the human brain and psyche, influenced by natural selection, have developed over millennia.
According to Harrison's research, published in the Journal of Forensic Psychiatry and Psychology, the female serial killers "knew all or most of their victims, and most were related to them".
In all cases, "they targeted at least one victim who was a child, elderly, or infirm — those who had little chance of fighting back", and in most cases, they killed primarily for money.
Men, on the other hand, have been shown through research to kill mainly for sex.
"This," Harrison says, "aligns with evolutionary psychological theory."
Also, according to earlier research, male serial killers "tend to stalk and kill strangers", whereas women "tend to kill people they know".
Harrison says it seems that male serial killers are "hunters", whereas women who kill are "gatherers".
In South Africa new research carried out on 108 women in local prisons has confirmed what other international studies are finding: that female psychopathy is ridden with grey areas that defy both the labels of medical textbooks and the public fascination with two-dimensional villains.
The study found that women psychopaths have a greater tendency to exhibit certain other personality disorders than their non-psychopathic counterparts do.Deadly scissors
She was only 18 years old, but in 1974 Marlene Lehnberg and Marthinus Choegoe murdered her lover's wife by stabbing her with a pair of scissors. The victim, Susanna van der Linde, was a mother of three.
Her husband, Christiaan, was 30 years older than Lehnberg and her boss at the Red Cross Children's Hospital in Cape Town. The two had a secret affair and would meet regularly at Rondebosch Common near the hospital.
Lehnberg met Choegoe at the hospital and pounced on his vulnerability as a patient: he had lost his leg in a car accident and had come to the hospital to have a prosthetic limb fitted.
He was unemployed and depressed, and despite his reluctance, Lehnberg convinced him to help carry out the murder. Susanna's body was found by her daughter.
The two killers were both sentenced to death, but the sentences were later set aside. Lehnberg was sentenced to 20 years imprisonment, of which she served 11 years. Choegoe got 15 years but was released in 1986. 
In 2015, Lehnberg, who had breast cancer and osteoporosis, committed suicide...