The 22-year-old, from Coolock in Dublin, is being held in Northern Ireland after going on the run.

Ranert was murdered close to Dublin airport on 30 April.

Detectives believe a group of four local youths approached the 28-year-old, who was in his car with his girlfriend in a lay-by popular with courting couples.

They intended to steal his mobile phone, and when he refused to hand it over they kicked in the driver's window and gave him a severe beating.

He died later from his injuries.

The gang subsequently stole Ranert's car and set it alight at a halting site in Coolock. Three of the men were arrested within 24 hours but a fourth man disappeared.

It has now emerged that he managed to source a fake passport and travelled to Belfast where he boarded a flight to Malaga.

He stayed there for two weeks and when he arrived back in Belfast he was detained by immigration officials who queried the authenticity of his passport. It was discovered that the passport was false and he was detained.

He has appeared in a Belfast court twice and has been remanded in custody.

He has agreed to cooperate with the investigation and detectives plan to travel north to interview him later in the week.

A file on the involvement of the other three men is being prepared for the DPP and will be sent after the fourth man is interviewed. It is understood there is forensic evidence to link several of the gang to the crime scene.