A European arrest warrant has been issued for Timmy Donovan who is wanted in connection with the murder of Merseyside Police officer PC Neil Doyle.
Donovan, who is also known as Timmy O'Sullivan and is from the Huyton area, Merseyside, is thought to have left the country for Spain.
Police believe the 30-year-old left the country at about 8.30pm on Friday, 19 December, through the Eurotunnel and that he was driving a five door grey Mercedes A180 (registration YE62 NWG).
Donovan is described as 5ft 8in tall, of broad build, with dark brown hair and blue eyes and has a Liverpool accent.
Detectives believe that Donovan is in Europe, possibly Spain, and are working with the National Crime Agency, Europol and European police forces in a bid to locate him.
Off-duty PC Doyle, 36, was out with two colleagues when they were allegedly targeted and assaulted because of their job at a Christmas party at Colquitt Street, near Liverpool city centre, at about 3.15am on 19 December.
A post mortem revealed he died of a fatal bleed around the brain after major blood vessels were damaged.