Michael Fegruson was shot dead in Derry in 1993.
A man has been arrested in connection with the murder of an RUC officers in Derry's city centre in 1993.
Constable Michael Ferguson, from Omagh, was shot twice, at close range, in the back of the head by an IRA gunman in Shipquay Street on January 23, 1993.
The 21-year-old Catholic policeman was on duty at the time and was taken to Altnagevlin Hospital but died from his injuries.
One man was jailed in 2015 in connection with the murder.
The PSNI today said that detectives from the PSNI's Legacy Investigation Branch arrested a 64-year-old man in Derry on Monday.
He is being held under the Terrorism Act and has been taken to Musgrave Police Station for questioning.
Subscribe or register today to discover more from DonegalLive.ie
Buy the e-paper of the Donegal Democrat, Donegal People's Press, Donegal Post and Inish Times here for instant access to Donegal's premier news titles.
Keep up with the latest news from Donegal with our daily newsletter featuring the most important stories of the day delivered to your inbox every evening at 5pm.