Most prolific murder ring

The most murders carried out by members of a mutually supportive group is at least 40, committed by the "Angel Makers of Nagyrév" in Hungary between 1911 and 1929. The members of this group were women who poisoned their husbands and other family members using arsenic supplied by the village's midwife, Zsuzsanna Fazekas. A total of 29 women were put on trial for the murders between 1929 and 1931, but just 16 were convicted. An inquest held in the early 1930s identified another 82 deaths in the area as suspicious, and it was believed that there may have been many more.

Nagyrév is a small village located around 25 km to the south of Szolnok in central Hungary. It lies on a narrow peninsula between the meandering river Tisa and an oxbow lake, connected to neighbouring villages by dirt roads that were impassable for much of the year. At the time of the killings, it was a rural and impoverished settlement of about 1,500 people where the routine of daily life had not changed significantly in centuries.

The village had no doctor, and its only point of contact with the official apparatus of the Austro-Hungarian state was the county gendarme, who visited Nagyrév every few weeks to hear grievances and take official reports. As a consequence of this isolation, Zsuzsanna Fazekas served not only as the village midwife, but also its de-facto doctor, counsellor and matchmaker. Many referred to her as the tudósasszony or "wise woman", a term historically associated with witches.

The earliest murders ascribed to the women of Nagyrév occurred in 1911, around the time that Fazekas arrived in the village. However, while she would become a key figure in the poisoning ring, it's not clear that she instigated it. The seemingly undetectable nature of arsenic was known to the women of the region, and there had been high-profile poisonings in the area before. The most notable was the "Mari Jáger Affair", a series of arsenic poisonings that occurred in the village of Hódmezővásárhely (around 60 km south of Nagyrév) in 1894. The driving force behind that series of killings was the eponymous Mari Jáger, also the village midwife.

The women of the town appear to have formed a mutually supportive group who encouraged and helped cover up each other's murders. Zsuzsanna Fazekas was a charismatic, well-respected figure whose views on the morality and necessity of the killings reassured the other members of the group. She also provided the arsenic, which she distilled by boiling down arsenic-laced flypaper.

Arsenic was, for many years, regarded as the perfect murder weapon. It is an odourless, tasteless and colourless substance that can be easily added to food or drink unnoticed. It acts relatively slowly, and in a way that is easily mistaken for many common maladies of the era, such as typhoid, alcohol poisoning or cholera. At the time of the murders, it was also extremely cheap and readily available either as a pure salt (for use as a pesticide) or as an ingredient in household products. In a village with no doctor and where the men were often in poor health, the Angel Makers were able to kill with impunity.

This came to an end in late June 1929, when the Szolnoki Újság newspaper published an anonymous letter, written by a citizen of Nagyrév, accusing the women of the village of murdering their husbands. The police arrived shortly after, and quickly realized that there seemed to be foul play involved in many of the deaths.

Two country doctors, Imre Orsós and Izodor Kánitz, were brought in to carry out the autopsies of the exhumed villagers. In most cases, years, or even decades, had elapsed since the alleged crimes, so there often wasn't much of a body to study. They were helped however, by arsenic's great drawback as a murder weapon; because it is a heavy metal and relatively nonreactive, it remains present in the tissues of its victims long after death, and can even be reliably detected in the burial clothes, coffin materials or surrounding soil after the body has decomposed.

A total of 29 women were charged with murder, and two men – husbands of accused women – were charged with conspiracy. Zsuzsanna Fazekas, ostracized by the community and under suspicion of murder, committed suicide before she could be arrested. Only 16 of those charged were actually convicted however, as beyond the chemical evidence of arsenic in the graves, in most cases there was nothing to connect them to the crime.