The authorities said one of the boys had been running errands for the 83-year-old victim, identified as Edeltraut B., in exchange for pocket money for about four months. But in February the two quarrelled at her Milbertshofen district apartment and the boy allegedly kicked her several times in the leg.

Police reported that the pensioner, who suffers from dementia, then cut off contact to the boy without reporting the altercation, and didn’t see him again until this Monday afternoon, when he rang her doorbell with a friend.

At a press conference in Munich on Wednesday, police described how the two boys forced their way into the woman’s home, then tortured her by forcing her to drink shaving cream and half a bottle of schnapps – ramming the bottle into her teeth when she refused, then urinating in the bottle. They also allegedly kicked her in the belly and upper body, poured liquid spices in her eyes and urinated on her while she lay on the ground.

“We believe it lasted for several hours,” chief detective Frank Hellwig said.

Both boys were already known to authorities as troublemakers, but did not have a record of violence.

“They both deny any involvement in the crime and implicate each other,” Hellwig said.

Edeltraut B. did not suffer life-threatening injuries, but she remains hospitalised and doctors are uncertain whether she will suffer permanent damage to her eyes. However, neither boy will be be legally punished as minors.

“They are not criminally accountable and can’t be prosecuted,” Hellwig added.