A Marblehead man was sentenced to three months in a house of correction this week for head-butting an MBTA bus driver last year, Suffolk County District Attorney Daniel F. Conley said today.

“The Members and Executive Board of Local 589 applaud the MBTA police and district attorney Dan Conley for holding people accountable for assaults on transit workers,” said President John Lee of the Boston Carmen’s Union, Local 589.

John Kerivan pleaded guilty to assault and battery on a public employee yesterday as his trial was scheduled to begin in Chelsea District Court. Assistant District Attorney Thomas Ozbolt recommended that he serve a year and a half behind bars; Judge Benjamin Barnes imposed the lower amount, which was greater than the suspended sentence that the defendant requested.

“No one should have to accept violence as part of their job,” Conley said. “That includes bus drivers. We’ll work hand in hand with Transit Police to identify, apprehend, and prosecute anyone who assaults an MBTA employee.”

Had the case proceeded to trial, Ozbolt would have introduced evidence and testimony to prove that Kerivan struck the driver on board a bus as it picked up passengers at Wonderland station on the night of July 23, 2012.

Specifically, Ozbolt would have shown that the driver pulled into the station at about 10:00 p.m. Among those waiting was Kerivan, who began screaming at the driver as soon as he boarded the bus. When the bus driver tried to calm him, the evidence would have shown, Kerivan head-butted him, knocking the driver off balance and disorienting him.

MBTA Transit Police found Kerivan in the station a short time later and took him into custody. The driver was released from duty for the day and received treatment at Massachusetts General Hospital.