It will take months before the process to extradite Gerard Hutch is complete, according to a former Assistant Garda Commissioner for the Dublin metropolitan area.
The 58-year-old, known as 'The Monk', was arrested in Spain on foot of a European Arrest Warrant and is currently in Spanish police custody.
His extradition was sought by the Garda team in Ballymun, which has been investigating the murder of David Byrne at the Regency Hotel in Dublin in February 2016.
"It's part of a process but it's a significant part of it in terms of who the person is," said Pat Leahy.
"We can't determine what the outcome of that process will be yet. From the time the warrant was issued and executed is not very long actually.
"I think a lot of people will be surprised actually that is came to fruition as quickly as it has. But the process now is about setting it in stone and all the legal requirements that are in a democracy will be put in place to protect the person that is the subject of the warrant."
Mr Leahy said a person who is the subject of the European Arrest Warrant will be offered an opportunity to surrender of their own volition immediately but that is unlikely.
"What happens then is that within 21 days the actual hearing process has to commence.
"There could be adjournments and habeas corpus applications, evidence will be heard on both sides, so it can go on for quite a time.
"So, I estimate that it will be around three months before we see any end in sight in relation to this," Mr Leahy said.
Mr Leahy said this is not a warrant that brings a person home for the purpose of an investigation.
It is either to serve a sentence if the person skipped bail or to face trial, he said.
A defence solicitor has said that if Mr Hutch consents to surrender he "could be back within the country within a short number of weeks."
However Fiona Baxter from Baxter Mimnagh Solicitors said that if Mr Hutch contests the warrant "he will be entitled to raise what's known as points of objection and if that's the case it could take up to 90 days before there is a final determination by the Spanish authorities"