A solicitor at the firm acting for Abu Hamza, the Muslim cleric fighting deportation, faces jail after being convicted of perverting the cause of justice in a separate case.
Maya Devani, of Arani & Co., which is representing Hamza, was found guilty of smuggling a letter out of a London jail to help a gunman accused of shooting a trial witness.
She was convicted at the Old Bailey today and will be sentenced at a later date when she faces an unlimited jail term.
Her client, Timothy Merchant, was convicted of two charges of attempted murder and was remanded for pre-sentence reports.
Devani was representing Merchant, 29, who was being held in Belmarsh Prison, south-east London, facing the two attempted murder charges after a street shooting.
Mark Dennis, the prosecutor, said Devani was involved "in a dishonest attempt to create a false defence" for Merchant by leaving the prison with his "written instructions" for an alibi to distance himself from the getaway car.
Days after Merchant?s younger brother was sentenced to nine years for a hold-up at a convenience store, a witness in the case was hit by five bullets as he sat in a car.
Mr Dennis said the victim was lucky to survive Merchant?s "act of retaliation".
When Merchant realised that an important piece of evidence allegedly linking him with the attack was found in a car, he recruited his solicitor to help him.
Devani, 26, from Middlesex, denied attempting to pervert the course of justice. She told the court she had not known what was in the letter until after she was charged and that she had no reason to put her career at risk to help Merchant.
A spokesman for the Law Society said her appearance before a professional disciplinary tribunal, which has the power to strike her off, was "inevitable."
Merchant, from Chelsea, South West London, denied two charges of attempted murder following a shooting near King?s Cross, central London, in August 2004 and attempting to pervert justice. He was also convicted of the second charge. The pair will be sentenced on 24 July. Devani?s solicitor, Burton Copeland partner Brian Spiro, said she will appeal.