William Bern Bell, 29, of Nunns Lane, pleaded guilty to a charge of sexually touching another person without consent and possession of cannabis, and represented himself in court.

According to police Bell was drinking with friends at a pub in Summer Street and the victim was also there with friends.

While one of his friends was talking with the woman, who Bell did not know, and her friends, Bell walked up from behind her rubbed up against her and moved both hands around her chest and groped her breasts.

The victim tensed up and Bell was pushed off and told his actions were "not okay" but he refused to leave and tried to touch her shoulder and later got into a tussle with the victim's husband.

Police were called and when they arrested him found him to be in possession of 15.6 grams of cannabis leaf which he said was supposed to last him six months.

"It was just a drunken mistaken act, I don't know what got into me," Bell said.

Magistrate David Day pointed out to Bell that the woman was a stranger.

"She can't see you coming because you came up behind... suggesting that for some reason you thought it was okay to do so," Mr Day said.

Mr Day said it was a serious matter and crossed the custodial threshold so he gave Bell a seven-month jail sentence with three-month non-parole period from November 25 to February 22 for squeezing the woman's breasts. It is Bell's first time in custody.

He was also convicted without further penalty for possession of the cannabis.