Police allege Kristy Louise McGuckin held police at bay at length while armed with a serrated knife and a syringe.

She was charged with one count of possessing a knife without a reasonable excuse following the ordeal.

Police allege McGuckin became agitated on a bus at about 8.30pm on Wednesday, calling triple-0 and Telstra. The ACT Magistrates Court heard she had a dispute with the bus driver, refusing to purchase a fare or leave the bus.

Police then became aware of her presence at the Canberra Centre near the Sunglass Hut stall off the City Walk entrance. They had received reports a woman was waving a knife around.

It is believed McGuckin was armed with a 20cm serrated knife and had threatened to jump from the building. She also pulled a syringe from her pocket and threatened to inject air into her throat.

Police eventually managed to subdue her at about 1.30am yesterday.

They reported McGuckin remained agitated and was uncontrollable, aggressive and violent.

During the hearing before Magistrate Maria Doogan, McGuckin interjected regularly, disagreeing with some of the evidence submitted.

Magistrate Doogan ordered McGuckin undergo a psychiatric assessment at Canberra Hospital.