Vandals smashed the rear window of a police car which was parked in a Daventry street.
A large stone was thrown through the back window of the Vauxhall Astra while it was parked in Tovey Drive sometime between 5pm and 6pm on Thursday, December 17.
Witnesses, or anyone who knows anything about this incident can call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.