A German federal court said Monday it has rejected a former Syrian secret police officer’s appeal against his conviction for overseeing the abuse of detainees at a jail in his homeland.

Anwar Raslan was convicted of crimes against humanity by a court in the western German city of Koblenz in January 2022, a decision that was described as “historic” by the U.N. human rights chief at the time. He was sentenced to life in prison.

Judges concluded that the former colonel was in charge of interrogations at a facility in Douma, just outside Damascus, known as Al-Khatib, or Branch 251, where suspected opposition protesters were detained.

German prosecutors alleged that Raslan supervised the “systematic and brutal torture” of more than 4,000 prisoners between April 2011 and September 2012, resulting in the deaths of at least 58 people. Judges ruled that there was evidence to hold him responsible for 27 deaths.

The Federal Court of Justice said it found no “legal error to the detriment of the accused” and rejected “procedural objections.”

Raslan’s conviction followed a verdict in February 2021 against a junior officer, Eyad al-Gharib, who was convicted of being an accessory to crimes against humanity and sentenced by the Koblenz court to 4 1/2 years in prison.

Both men were arrested in Germany in 2019, years after seeking asylum in the country. The federal court rejected al-Gharib’s appeal in 2022.