Taha Al J., 29, stood trial in Frankfurt after he was arrested in Greece on terror-related charges in 2019. He fled to Athens from Iraq via Turkey a year earlier, the German court said in a statement.
The court found that he joined the Daesh* terrorist group in Syria in 2015 as it was expanding its territorial hold across the region.
While in Syria, the suspect bought a Yazidi woman and her five-year-old daughter, who were captured during a Daesh* raid on a Yazidi village in Sinjar in northern Iraq in 2014.
The Yazidis were kept as slaves in his Fallujah home in Iraq, doing all household chores. The man repeatedly beat the two and once "lent" the little girl to his male friend for a night.
The girl died from a heat stroke after the suspect left her tied outside home in scorching sunlight without access to water as a form of punishment.
Taha Al J. collapsed after hearing the verdict, the Sueddeutsche newspaper reported. The trial was briefly suspended.
A UN expert team labelled Daesh* crimes against Yazidis as genocide in May. It systematically persecuted Yazidis, of whom thousands were killed, raped and tortured by Daesh* fighters. Hundreds of thousands were forced to flee their homes.
*Daesh (IS/ISIS/ISIL) is a terrorist organisation banned in Russia.