Thomas David Lukas Olsen was born on April 11, 1975, in Frankfurt am Main, West Germany. In 2015, he changed his name from Magnus Gäfgen to Thomas David Lukas Olsen. His new name was reportedly inspired by a fictional Danish criminal named Egon Olsen. 

On September 27, 2002, in Frankfurt, Germany, Magnus Gäfgen kidnapped 11-year-old Jakob von Metzler. His intention was to demand a ransom from Jakob's wealthy family, who were known in the banking industry. After taking Jakob to his apartment, Gäfgen killed him. Days later, he contacted Jakob's parents and demanded a ransom of one million euros.

The police were aware of Gäfgen's actions. They observed him when he went to pick up the ransom but found that he had not released Jakob, who was already dead. After several hours, Gäfgen was arrested. During the interrogation, police used threats of torture to persuade him to confess. This tactic led him to disclose where he had hidden Jakob's body.

Legal proceedings began in July 2003. The court found Gäfgen guilty of murder and sentenced him to life imprisonment. The court noted the severity of his crimes, meaning he would not be eligible for early release. Gäfgen's appeals to higher courts were rejected in later years.

One of the police officials involved, Wolfgang Daschner, was later convicted for his role in the interrogation tactics and received a suspended sentence. In 2005, Gäfgen made a complaint against Germany at the European Court of Human Rights. He won part of the case, as the court found that his treatment had violated laws against torture but ruled that his right to a fair trial had not been breached.

Gäfgen has been incarcerated in Schwalmstadt Prison since his sentencing. While in prison, he completed a law exam and later published an autobiography. In 2017, he sought early release on probation, but officials determined he remained a danger to society and denied his request. The prison set a new minimum sentence, meaning Gäfgen would not be eligible for release until September 2025.