Mr Mitchell, 49, was made the subject of a controversial European Arrest Warrant and faces being sent back to prison despite being cleared of the charges by three judges in 1995.
The father-of-two spent a year in prison over claims he threw Andre Jorling over a 12ft sea wall, leaving him paralysed from the waist down.
He was accused of attempted murder along with Mr Tozer during their fishing trip to the Algarve in 1994.
But police were believed to have ignored the description of Mr Jorling's attackers given by the then 26-year-old victim, which did not match with Mr Mitchell and his friend, according to the Daily Mail.
After a year in custody, Mr Mitchell, a former Scots Guardsman from Canterbury, Kent, was released as a free man.
But Portuguese authorities have now applied to have him extradited, branding him a "fugitive" and even accusing him of first degree murder despite Mr Jorling living on after he was injured.
Miss Jenny Agnew, representing Mr Mitchell at Westminster Magistrates' Court, said: "We need clarification as to why the arrest warrant says first degree murder when the victim is still alive."
She added: "He was acquitted of murder in 1995. He was also remanded in custody for one year and two weeks for this offence. We would like an outline of why this European Arrest Warrant has been issued."
The warrants, which allow for the arrest of British citizens for crimes anywhere in the EU, have been criticised for targeting people suspected of minor offences or innocent people who then face the prospect of a lengthy battle to clear their name.
Mr Mitchell's wife Laura told the Mail: "I am frightened to death about what will happen to him. He can't go back to Portugal after the way they treated him. He is an innocent man.
"They said they had been issued with EU arrest warrants and they just took him. It was so quick. He was so shocked. The police didn't warn us it was going to happen."
Natasha Draycott, representing the Portuguese judicial authority, told the court: "The friends intended to harm Mr Jorling because of his nationality and because he had been socialising with two women which had upset them.
"He was pushed over the wall. He was completely paralysed and unable to work as a result."
She claimed Mr Mitchell was a fugitive because he knew about the warrant.
The hearing was adjourned.