Martha Marek was born on October 10, 1897, in Vienna, Austria. She was orphaned at a young age, which led her to be raised by a relatively poor family. Growing up without her parents, Martha faced many challenges in her early life.

In 1919, when Martha was 22, she worked in a dress shop. It was during this time that she met Mortice Fritch, a wealthy 74-year-old department store owner. Fritch was 50 years older than Martha. The following year, their relationship became romantic, and Fritch sent Martha to prestigious finishing schools in France and England. These experiences gave her a taste of a luxurious lifestyle.

After her education, Martha returned to Vienna to live with Fritch. However, she soon became involved in an affair with another man named Emil Marek, who was an engineer. In August 1923, Fritch passed away and left Martha his estate in the Vienna Woods. Martha married Emil in 1924.

The couple enjoyed a life of relative wealth for a time, but their funds quickly diminished. By 1925, they faced financial difficulties. That June, Emil had a serious accident while chopping wood and lost his leg. This incident came just after Martha had taken out an insurance policy on him, which raised suspicions.

The couple began to attract media attention due to the strange circumstances surrounding Emil’s injury and the insurance claim. A lawsuit followed, and forensic evidence revealed that Emil had deliberately harmed himself. In April 1927, the court found them not guilty of insurance fraud but guilty of bribing officials, resulting in a four-month prison sentence. The public largely sympathized with Martha during this time.

After their release, the Mareks' financial situation remained poor, and they eventually moved to Algiers. They had two children while living there. Emil died unexpectedly in July 1932, which shifted public focus back to Martha, the grieving widow.

Martha Marek was involved in a series of murders that spanned from 1932 to 1937. After the unexpected death of her husband, Emil, on July 31, 1932, she attracted public attention as a grieving widow. Shortly after, her two children began showing similar symptoms to those of their father, and her seven-year-old daughter died after Martha had taken out life insurance policies on them. This tragedy helped garner sympathy and financial support from the community.

In 1934, Martha inherited money from her aunt, Susanne Löwenstein, who also died soon after. Once she spent her inheritance, she took in Felicitas Kittenberger, a tailor, as a subtenant. Martha persuaded Kittenberger to take out a life insurance policy in her favor. Kittenberger died shortly after, raising suspicions from her son, who reported his concerns.

Investigators looked into the deaths of all four victims and found that they had been poisoned with thallium from a product called Zelio, which was available at the time. Following another insurance fraud, where Martha claimed expensive paintings were stolen, she was arrested. The investigation into these cases led to the exhumation of the bodies and confirmed the presence of poison.

During her trial, Martha pretended to have seizures and blindness and was brought to court in a special chair. On May 19, 1938, the jury found her guilty of murder, and the court sentenced her to death. Many believed she would be pardoned, as was common for women in similar situations. However, after Austria was annexed by the German Reich, Adolf Hitler denied her a reprieve.

Martha Marek was executed on December 6, 1938, becoming the first person to be executed by guillotine in Vienna after it was brought from Berlin. The execution took place at the Vienna Regional Court, carried out by the executioner Johann Reichhart.