Authorities in Troy, Mich., report Breanna Calvin was stopped at a courthouse security check when she set off the metal detector.
Deputies searched her purse and say they found a knife with an attached set of brass knuckles.
The 18-year-old was headed to court in a retail fraud case,
Now, she's been charged with a felony, possession of a dangerous weapon.
Oakland County Undersheriff Mike McCabe says the young woman told deputies her boyfriend gave her the weapon for protection on the streets.