Shane O'Brien is suspected of murder Credit: Met Police
Europol, which has announced Europe's most wanted, said O'Brien is wanted for murder and grievous bodily injury.
A reward of up to £50,000 is available for information leading to the arrest and prosecution of O'Brien.
In February 2017, he was arrested in Prague for criminal damage and assault but used the Italian alias of Enzo Mellonceli, supported by false documentation, and was bailed pending further enquiries.
An image taken then shows he has grown his hair, has a full beard and has a distinctive new tattoo of an owl holding a skull, which covers up his previous "Shannon 15-04-06" tattoo.