Martin Ney was born on December 12, 1970, in Bremen, West Germany, which is now part of modern Germany. He grew up in a time when the country was going through significant changes. Details about his early family life and childhood are not widely documented, yet some aspects of his personality were noted.

As a teenager, Ney had a troubled period. At the age of 17, he threatened to kidnap children, which raised concerns about his behavior. This incident showed that he had issues even at a young age. By the time he turned 18, he was convicted of extortion involving a large sum of money. This led to a criminal record, but it was expunged when he turned 24.

Despite his past, Ney was able to apply for a role as a foster parent in 1995. He lived alone at that time and was studying. The welfare office accepted him as a foster father because there was a lack of available candidates. He gained custody of a 12-year-old boy who lived with him until he became an adult. This boy reportedly was not harmed during their time together.

Ney studied pedagogy and even worked as a youth worker. This job allowed him to interact with children, which would later play a role in his life. He had a position at a daycare where he became familiar with several children, including some who would become his victims. Despite his education and career, Ney faced legal issues throughout the years.

In 2005, he was charged with minor sexual abuse cases, which were settled through financial compensation. He also attempted to blackmail a social worker, leading to a brief probation sentence for attempted extortion. Despite these events, Ney continued to lead a life that presented little indication of his future actions.

In 1992, Martin Ney began a series of sexual assaults on boys in northern Germany. He was known for attacking at night while wearing a mask. His first known contact occurred in a children's home in Hepstedt, where a student found him in an empty dormitory. Ney fled the scene, but over the next few months, several boys reported attempted sexual abuse. By August of that year, he started to sexually abuse children at school camps.

Ney continued his attacks in various boarding schools, with notable incidents in Schullandheim Badenstadt. On one occasion, he was reported to have touched a nine-year-old boy inappropriately. He struck again in 1994 and 1995, with boys often resisting his advances. In June 1995, he sexually abused a ten-year-old exchange student in Wulsbüttel, continuing a pattern of abuse that saw multiple attempts to sexually assault children.

The crime escalated in 1992 when 13-year-old Stefan Jahr disappeared from a boarding school in Scheeßel. Nearly a month later, his body was found buried with his hands tied. Later, in 1995, eight-year-old Dennis Rostel disappeared from a camp. His body was discovered in Denmark two weeks after his disappearance. In 2001, Ney murdered nine-year-old Dennis Klein, whose body was found weeks later in nearby shrubbery.

Ney's crimes did not stop there. In April 2004, he was connected to the murder of Jonathan Coulom in France, who also went missing. His body was discovered months later, undressed and handcuffed, suggesting Ney's ongoing pattern of violence and control over his victims.

Despite various police investigations and public appeals for information, Ney remained undetected for years. It was not until 2011 that a previous victim identified him, leading to his arrest. During interrogations, Ney admitted to killing Jahr, Rostel, and Klein, and confessed to abusing around 40 other children.

After his arrest, the evidence compiled against Ney included a history of sexual abuse and kidnapping threats made years prior. In February 2012, he was convicted of three murders and multiple counts of sexual abuse and sentenced to life in prison. Ney’s case continued to evolve when, in January 2021, he was extradited to France to face charges related to Coulom’s murder.