Kenneth Renney, 30, was held after a group disturbance in and around Roedean Road, Hylton Red House, on the morning of Saturday, December 4.
Renney, of Marley Crescent, Marley Potts, remained calm until seeing his sister put in handcuffs as part of the same police clean-up operation.
He headbutted the vehicle several times and kicked and damaged an interior panel, South Tyneside Magistrates’ Court heard.
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Prosecutor Bushra Begum said: “A number of officers were required to attend Roedean Road.
“There was a disturbance involving multiple people. There was a report of a fight involving a knife, and a number of people had injuries.
“The defendant was arrested because he appeared to have some injuries that he couldn’t account for.
“This particular offence falls when he is placed in the back of a police vehicle, which he headbutts when his sister is being arrested.
“He also kicks at a panel, which causes the window to come away. That’s effectively the damage.
“I don’t have a value from the police of the damage, but the entire panel appears to come away.”
Renney, who had six previous convictions but none since an assault in 2013, pleaded guilty to causing criminal damage.
Defence solicitor Paul McAlindon said: “It’s a guilty plea at the first opportunity. The prosecution case is fully accepted.
“The police are called to what appears to be a disturbance. He sat quite quietly in the back of the police vehicle.
“When police brought out his sister in handcuffs, it upset him. He banged his head against the window a few times.
“There doesn’t seem to be a lot of damage. It is something that was committed on impulse.
“The officers ask him to calm down, it’s no more than that. He lost his temper when his sister was arrested.
“It appears that she may have been the victim rather than the perpetrator.”
District Judge Paul Currer handed Renney a 12-month conditional discharge, with £85 court costs and a £22 victim surcharge.