Derwentside District Council planning officer Harry Collinson was murdered while carrying out enforcement duties on an unauthorised structure in County Durham in June 1991.
A plaque erected after his death at the Consett Civic Centre has now been moved to County Hall in Durham.
A dedication ceremony took place at County Hall this morning, attended by the niece of Collinson, Lisa Foster, who was representing the family.
Durham County Council chairman councillor Dennis Morgan said: "It was a day that rocked the very fabric of local government and will be etched in many people’s memories for all time.
"I am pleased that so many of Harry’s colleagues are with us today and Lisa Foster and her husband Neil - our thoughts and prayers are with you and the family."
Albert Dryden was sentenced to life for the killing and for wounding a policeman and a BBC journalist in the same incident.