Burke (21) faces the long sentence after being found guilty on Friday of stabbing Abraham Baez (24) in the neck with a kitchen knife during a street brawl.
His lawyer said the "devastated" Dubliner maintains his innocence and will launch an appeal.
Mr Baez died from massive blood loss after being knifed during a 6am fight in Playa de las Americas on 30 April, 2010.
A jury unanimously found Burke guilty of murder at a court in the island's capital Santa Cruz.
Yesterday, his lawyer Avelino Miguez said none of the witnesses to the fight saw his client carrying a knife or stabbing Mr Baez.
Police found no traces of the Spaniard's blood on Burke's clothes even though doctors said he would have lost at least half a litre of blood per minute after his carotid artery was severed by the knife.
Crucially the jury accepted prosecution claims Burke hid the knife in the palm of his hand, with the blade protruding between his fingers, as he attacked Mr Baez.
That allowed them to convict the Irishman of murder rather than the lesser charge of manslaughter.
But a pathologist told the court the wound to Mr Baez neck was caused by the knife being held in a normal, downward stabbing motion.
Mr Miguez said: "We will appeal against the conviction."
The lawyer also hopes to use a little-used law to have his client sentenced as a minor, even though he was 18 at the time of the killing.
Mr Burke's family fear for his safety at the prison in Tenerife where he is being held.
During the one-week trial his lawyer complained to the court after people in the public gallery were seen making a throat-slitting gesture at the defendant.
A family friend said: "We're terrified what might happen to Keith while he's in prison. We're sick with worry."
Burke told his family "Don't worry, I'll be okay" as he was led to the cells following his conviction.
Judge Fernando Paredes will sentence him to between 15 and 20 years at a later date.
His then girlfriend Sara Stuart (30), also from Dublin, was found guilty of wounding the dead man's girlfriend, Laura Negrin, during the same fight.
But she is expected to get a suspended sentence after being cleared of the more serious charge of wounding her with a rock.
Outside court Mr Baez's family said they were satisfied justice had been done. Mother Maria Teresa said: "My son was only 24 and had a good future in front of him. Nothing will bring my beautiful son Abraham back, but we came here to see justice and justice has been done."
All four people involved in the fight had been drinking heavily the night before the tragedy.
Burke claimed in court he was attacked by the Spaniard, who he believed was trying to rob him.
He admitted carrying a knife for protection but said it never left his pocket.
Police later found a knife, believed to be the murder weapon, with Burke's blood on it, near the murder scene.
Burke also had cuts on his hand "consistent with having used a knife" in a fight, the court was told.
While on remand he wrote daily love letters to his then girlfriend Ms Stuart, appearing to confess to the killing.
In one he wrote: "I will be sentenced to 15 years and to be honest I deserve it."