Bradley Steven Gibson, 26, yesterday pleaded guilty in the Ballarat Magistrates Court to possessing cannabis, assaulting police and being drunk in a public place.

Police Prosecutor Senior Constable Kerry Bourke told the court Gibson had been seen by police being pushed in a shopping trolley near Eastwood St in November last year.

Sen Const Bourke, said the person pushing the trolley returned it to the supermarket when asked but police noticed Gibson was unsteady on his feet.

Gibson was taken to the Ballarat police station where he tried to head-butt sections of the custody area before being placed in a holding cell, Sen Const Bourke said.

The court heard Gibson then refused to take off a chain around his neck and when police tried to remove it he twice spat blood in the face of a policeman.

Gibson is currently serving a nine-month jail sentence for unrelated matters.

Magistrate Kay Robertson said she hoped Gibson was able to get back on track when he was released in January.

She sentenced him to 21-days imprisonment to be served concurrently with the jail sentence he is serving.