A man who allegedly beat his mentally-disabled stepdaughter to death should be jailed for 14 years and then sent for psychiatric treatment, the public prosecution service said on Wednesday.

Daniëlla van Bergen, who had the mental age of a nine-year-old, died at the age of 20 in 2013. Her mother and stepfather were arrested in their Groningen home shortly afterwards.

The prosecution claims the young woman was systematically beaten for weeks prior to her death. Blood traces were found all over the house. She had broken bones, a stab wound and bruises all over her body.

Evidence against her stepfather includes broken knuckles and bruises. Traces of the woman’s blood was found on his clothes and shoes, the prosecution said.

Daniëlla’s mother faces four years in jail for failing to stop her husband from killing her and calling for medical help.

Stepfather Geert W had earlier been jailed for raping and threating two stepdaughters from a previous relationship. He met Daniëlla’s mother during his time in prison, news agency ANP reports.

The family was known to social services but they had failed to take action to ensure the young woman’s safety, ANP says.