Olaf Däter was born on September 25, 1969, in Bremerhaven, West Germany. He was an illegitimate child and was adopted by his stepfather when he was just one year old. Däter grew up as an only child. He maintained a close relationship with his parents throughout his life. They often provided him with financial support during times of need. At the time of his later actions, he lived near his parents.

Däter completed his school education by earning a Mittlere Reife, a German qualification similar to a high school diploma. After finishing school, he tried for eight years to get a job as a gerontological nurse but had little success. He eventually joined the Bundeswehr, the German military, where he served in a medical unit. He held the rank of Oberfeldwebel until he finished his military career. Those who worked under him described him as bossy and meticulous when giving orders.

After his time in the military, Däter received training to become a nurse through a program in Cuxhaven with the German Armed Forces. He later got married, but the marriage did not last long and ended in divorce after just one year.

In June 2001, Olaf Däter committed a series of murders targeting elderly women. Over ten days, he killed five women and attempted to murder a sixth, who survived by fainting. Däter entered the homes of these women, using his previous experience as a geriatric nurse to gain their trust. This allowed him to move unopposed in their apartments.

Däter attacked his victims from behind and suffocated them by kneeling on them, which caused severe internal injuries. He was careful to rob them, but he typically only took cash, ignoring other valuables like jewelry. His methods allowed him to leave some crime scenes without a victim due to unexpected interruptions, such as nearby nurses.

After the final attack, he used the stolen money for a private flight with a girlfriend and her child. When he returned from the flight, police were waiting for him. They had suspected him of murder after a survivor named him as her attacker. The four previous victims were initially thought to have died from natural causes, but investigations changed after Däter confessed.

Däter had been fired from his job for stealing from patients. His past criminal behavior had been hidden from potential employers, allowing him to work as a nurse. After his arrest, the court sentenced him to life imprisonment, citing the seriousness of his crimes and his intent to continue if he had not been caught.