A former American football star who playfully slapped his attorney on the bottom has been sentenced to 30 days in prison, after a judge angrily rejected his no-jail plea.

Ex-NFL player Chad Johnson was expected to be handed a community service order and counselling over a probation violation in a domestic violence case after reaching an agreement with prosecutors.

But he incurred the wrath of Broward County Circuit Judge Kathleen McHugh after giving his lawyer Adam Swickle a light swat - as football players routinely do on the field - when asked whether he was satisfied with his attorney.

The courtroom erupted in laughter, at which point Judge McHugh halted proceedings and said she would not accept the deal.

She said: "I don't know that you're taking this whole thing seriously. I just saw you slap your attorney on the backside. Is there something funny about this?


Image: Judge McHugh and Johnson (Pic: Broward County Sheriff's Office)

"The whole courtroom was laughing. I'm not going to accept these plea negotiations. This isn't a joke."

Johnson, 35, tried to apologise and insisted he did not mean to disrespect the judge.

The former wide receiver was on probation after pleading no contest to head-butting his then-wife, TV reality star Evelyn Lozada, during an altercation last August.

She filed for divorce after a month of marriage, and Johnson was immediately released by the Miami Dolphins. He did not play at all last season.

"This is your courtroom. I have no intent to make this a joke. It's not funny," Johnson told the judge.

"My life is in a shambles right now and I try my best to laugh and keep a smile on my face."

Image: Johnson and his former wife Evelyn Lozada

But the judge, who could have given Johnson up to a year in jail, was not moved.

"It's not the first time he's behaved that way in my courtroom," she said.

Johnson, who was handcuffed and hauled away to jail, later wrote on his Twitter account: "Love me through the good and the bad because I'm gone love you regardless ... See you in 30."