A German female member of Islamic State is facing war crimes charges in her home country for letting a five-year-old girl die of thirst in the scorching sun.

The 27-year-old German citizen identified only as Jennifer W and her husband purchased the child as a household “slave” when living in then Isis-occupied Mosul in northern Iraq in 2015, German prosecutors said on Friday.

“After the girl fell ill and wet her mattress, the husband of the accused chained her up outside as punishment and let the child die of thirst in the scorching heat,” they said in a statement. “The accused allowed her husband to do so and did nothing to save the girl.”

The federal prosecutors said they had laid the charges of war crimes, murder and weapons offences on 14 December in a Munich court that deals with state security and terrorism cases.

W had first left Germany in August 2014 and travelled via Turkey and Syria to Iraq where she joined Isis the following month. Recruited to a vice squad of the group’s self-styled morality police, she would patrol the city parks of the Isis-occupied cities of Falluja and Mosul.

“Her task was to ensure that women comply with the behavioural and clothing regulations established by the terrorist organisation,” said the statement. For intimidation, the accused carried an assault rifle of the type Kalashnikov, a pistol and an explosives vest.”

W visited the German embassy in Ankara to apply for new identity papers in January 2016, months after the child’s death. Turkish security services arrested her when she left the mission and and she was extradited to Germany a few days later.

For lack of actionable evidence against her, she was initially allowed to return to her home in the state of Lower Saxony. “Since then her declared goal has been to return to the territory under Islamic State rule,” said the prosecutors. When she attempted to again travel to Syria in June, German police arrested her.

No date has been set yet for the start of the trial. If found guilty, she would face a life sentence.