Yvan Keller was born on December 13, 1960, in Wittenheim, Haut-Rhin, France. He was the youngest of nine children in a family that made baskets and lived as sedentary travelers. His father, Joseph, worked in the potash mines of Alsace. Keller's family life was challenging, primarily because his father made him work hard to help support the family. This environment contributed to instability in his early years. Tragically, his mother passed away at the age of 49.

Yvan's early life took a serious turn when, at the age of 17, he was arrested for stealing two antiques in Battenheim in 1981. As a result, he was sentenced to 10 years in prison for robbery. After spending several years behind bars, Keller was released in August 1989.

Following his release, Keller moved to Mulhouse, specifically to Rue de Verdun, where he settled in a quiet apartment within an old mansion. He established a small landscaping business called Alsa-Jardin. His clients appreciated his work and often recommended him. During this time, he lived a modest life with his first companion, Marina. However, they eventually separated, and he later found a new partner named Séverine.

Neighbors described Keller as helpful, friendly, and kind to animals. However, Marina claimed that he pressured her into prostitution due to his constant need for money. His lifestyle included a desire for luxury, frequent visits to casinos, and spending time in nice restaurants and hotels. There were also reports that during his relationship with Séverine, she was already seeing another man. Upon discovering this, Keller confronted the man and threatened him with a gun.

In January 1994, Yvan Keller was connected to his first known victim, Marie Winterholer, who was found dead in her bed at her home in Burnhaupt-le-Haut. A doctor concluded her death was natural, and she was issued a burial permit.

On March 12, 1994, another victim was discovered. Germain had gone to visit his 86-year-old mother, Ernestine Mang, only to find her dead in bed. He noted that the bedding was neatly arranged, which seemed unusual since Ernestine had difficulty moving.

Later, on April 27, 1994, 77-year-old Augusta Wassmer was also found dead in her bed, lying on her back. No signs of a break-in were found at her home. Her daughter, Marie-Françoise Roecklin, observed that the bed had been unusually well-made. The autopsy determined that Augusta died of cardiac arrest, likely caused by great fear. Marie-Françoise soon discovered that Augusta's bank card and house key were missing, with the card having been used to make withdrawals in Mulhouse.

After his arrest, Keller confessed to the murders of many elderly women. He claimed responsibility for up to 150 murders, although he was indicted for only five, specifically three in Haut-Rhin and two in Bas-Rhin. Investigators noted similarities to other unsolved cases, leading them to suspect he might have killed additional victims.

Keller, working as a landscape gardener, had an advantage in locating the homes of elderly people, which made it easier for him to commit his crimes. His pattern involved suffocating his victims in their beds and then making the bed look perfect, creating the illusion of a natural death.

Despite being denounced several times between 1993 and 2003, Keller was not arrested until a lengthy investigation. After his confession, he faced charges for his crimes, and more cases were opened for investigation based on his activities.

On September 22, 2006, while in custody at the Mulhouse High Court, Yvan Keller took his own life by hanging himself using his shoelaces in his cell.