Newspapers have been warned they risk impeding the course of justice if they vilify a suspect who is under arrest.

The Sun and Daily Mirror were today both found to have breached the Contempt of Court Act 1981 through their reporting of the investigation into the murder of Bristol woman Joanna Yeates.

Her landlord, Christopher Jefferies (pictured), was arrested five days after her body was found on Christmas Day last year but was released on unconditional bail on 1 January.

Vincent Tabak later confessed to manslaughter, leaving Jefferies exonerated entirely.

The contempt case was brought by Attorney General Dominic Grieve on the basis that if Jefferies had faced a trial, this could have been prejudiced because the articles in the Sun and Daily Mirror could have prevented potential defence witnesses from coming forward.

The Lord Chief Justice, Lord Judge, said two articles in the Mirror had ‘vilified’ Jefferies.

Both defendants claimed their articles had not created substantial risk of serious prejudice to any trial likely to take place nine months later, with memories fading in that time and the jury able to deliver unbiased verdicts.

But in their judgment, Lord Judge, Lord Justice Thomas and Mr Justice Owen said the actions of newspapers could harm the conduct of the trial itself, regardless of whether the jury has been prejudiced.

The judges said: ‘At the simplest level publication of such material may deter or discourage witnesses from coming forward and providing information helpful to the suspect, which may, (depending on the circumstances) help immediately to clear him of suspicion or enable his defence to be fully developed at trial.

‘This may arise, for example, because witnesses may be reluctant to be associated with or perceived to be a supporter of the suspect, or, again, because they may begin to doubt whether information apparently favourable to the suspect could possibly be correct.’

The judges have invited submissions from the Attorney-General and counsel for the two newspapers on penalty.