ALLEGHENY TWP — A Philadelphia teenager faces a hearing on charges she took a bite out of a staff member at a northern Butler County juvenile detention facility.

Valerie M. Santos, 18, is accused of biting the knee of the victim during at an altercation Aug. 1 at Western PA Child Care on Route 38 in Allegheny Township.

Police last week charged Santos with felony and misdemeanor assault and summary harassment.

The disturbance began when the teen refused to obey instructions at the facility, according to court documents, and spit on Jennifer Pelto, a clinical assistant.

Mid Atlantic Youth Services owns the secured facility that houses males and females from ages 16 to 21 who have been placed there following court disposition of their juvenile cases.

Police said the defendant also threw milk on Pelto and threatened to “beat” her.

At one point while scuffling with staff, Santos allegedly bit Pelto on the right knee. Police said the assault left the victim with a large bruise.

“Santos admitted to throwing milk on Pelto,” according to a police affidavit, “because Pelto was aggravating her and when staff restrained her she was defending herself.”

A preliminary hearing in the case is pending.