A "breathtakingly unprofessional" solicitor, who was filmed in a TV sting, has been jailed for three years.
Mr Lancaster had been a magistrate
David Lancaster, 56, of Havant, had denied, at Exeter Crown Court, inciting an undercover reporter to pervert the course of justice.
BBC South's Inside Out staged an advice session with Lancaster, who explained how to stop witnesses from testifying.
The former Warner, Goodman and Streat employee, "broke every rule in the book", the judge told him.
Judge Graham Cottle went on to say Lancaster had given "a breathtaking display of unprofessional conduct".
Royal Navy Commander
The court heard how journalist Neil Ansell, posing as a client, had been given false explanations to use when he returned to answer police bail.
Mr Ansell had claimed to have been arrested by police after being named as a cocaine supplier by a friend.
Lancaster was filmed telling Mr Ansell: "You could say that at the time he changed the 50 quid for me, he showed me this cocaine wrap and I was horrified.
"I daren't do drugs even if I wanted to because if I did, I'd lose my job, and I gave it straight back to him."
The senior defence lawyer is a retired Royal Navy Commander, serving on the royal yacht Britannia.
In December 2004, at the time of the offence, Lancaster was an equity partner for Warner Goodman and Streat in Portsmouth, but had also been a magistrate for four years.
Ian Curtis, managing director of solicitors Warner, Goodman and Streat, said he felt he could not comment on the court verdict.
Mr Curtis said: "David was expelled from the partnership more than 18 months ago. Since then he has had no involvement with the firm - nor have I had any involvement in the prosecution process."
Judge Cottle said: "It follows that if any member of the legal profession engages in behaviour that brings the system into disrepute, he threatens the deserved reputation of the criminal justice system, and this necessarily has an impact on fellow professionals.
"Your behaviour in this case totally undermines that deserved reputation."
Lancaster told the jury, interfering with justice "was the furthest thing from my mind."
When Lancaster was confronted by the BBC, with the conclusions of the investigation, he said he had done nothing wrong.
The jury decided Lancaster's advice to Mr Ansell had a tendency to pervert the course of a police investigation, and that he had advised him to use them with intent to do the same.