Mariëtte Sonjaleen Bosch was born in 1950 in South Africa. She was the daughter of a wealthy liquor store owner. Seeking a safer environment and better economic opportunities, she moved to Botswana with her husband, Justin Bosch, and their three children. The family settled in Phakalane, an affluent suburb of Gaborone, known for its expatriate community. Mariëtte became an active member of the Dutch Reformed Church and was well-regarded in social circles. Her life took a tragic turn when Justin died in a car accident in 1995, leaving her a widow.

Following her husband's death, Mariëtte began an affair with Marthinus "Tienie" Wolmarans, the husband of her close friend, Maria Magdalena "Ria" Wolmarans. The Wolmarans had experienced marital difficulties, having separated in 1993 and reconciled in 1994. Despite Tienie's promises to divorce Ria, the process was prolonged, leading to tension and impatience on Mariëtte's part.​

In June 1996, Mariëtte traveled to Pietersburg, South Africa, where she obtained a pistol from a friend. She smuggled the firearm into Botswana and, on the night of June 22, 1996, entered the Wolmarans' residence by climbing over a security wall. Inside, she confronted Ria and shot her twice, resulting in Ria's death. Initially, the police suspected a botched burglary, and the case remained unsolved for several months.

Suspicion eventually fell on Mariëtte due to a series of incriminating actions. She confided in her sister-in-law about her love for Tienie and handed over the murder weapon, which was later linked to the crime. Additionally, she ordered a wedding dress shortly after the murder, indicating plans to marry Tienie. These actions led to her arrest and subsequent trial.​

On December 13, 1999, Mariëtte was convicted of Ria's murder and sentenced to death. Her appeals were unsuccessful, and she was executed by hanging on March 31, 2001, at Gaborone Central Prison. Her execution marked her as the first white woman to be executed in Botswana and the fourth woman hanged since the country's independence. The case attracted significant international attention and was often referred to as "Botswana's White Mischief," drawing parallels to the infamous colonial-era scandal in Kenya.