Sun and Mirror in the dock over coverage of Joanna Yeates murder

The Sun and the Daily Mirror breached contempt of court laws during their coverage of the murder of Joanna Yeates in Bristol, the Attorney General told the High Court yesterday. Dominic Grieve QC said the nature of reporting from the two tabloids after the arrest of Ms Yeates' landlord Chris Jefferies was "so exceptional, memorable and adverse" that there was "substantial risk of serious prejudice" to any trial he might have faced.

The outcome of the case could have major implications for how newspapers cover crimes amid concern that some publications are pushing the limits of what can be reported as they struggle to compete with largely unregulated online competitors and 24-hour news.

Ms Yeates went missing on 17 December last year, prompting a huge amount of press coverage. Her frozen body was found on Christmas Day in nearby Failand.

Mr Jefferies, a former teacher in his 60s, who lived in the Clifton area of Bristol, was arrested on 30 December but was released on police bail. He has been cleared of any involvement in the murder of Ms Yeates. He has since issued separate libel proceedings against six national newspapers for their coverage of his arrest.

Three weeks after his release, Vincent Tabak, a 33-year-old Dutch citizen, was arrested on suspicion of murdering Ms Yeates. He has pleaded guilty to manslaughter and will face a full murder trial later this year.

The Attorney General went before three High Court judges – including the Lord Chief Justice, Lord Judge – to argue for an "order for committal or other appropriate penalty" against the publishers of The Sun and the Daily Mirror. If found in contempt, the publishers could face a fine or even a prison sentence.

The court yesterday heard how the case revolved around the publication of three articles. One was printed in the Daily Mirror on 31 December 2010. The other two were printed by both newspapers the next day.

The Attorney General admitted that the arrest of Mr Jefferies had prompted a deluge of negative publicity about the retired teacher. But he said the three articles had been "exceptionally adverse and hostile".

Mr Grieve said the reports referred to Mr Jefferies as a "sexually perverted voyeur", alleged he was a close friend of a paedophile and had previously stalked a women. An article in the Daily Mirror also alleged he might have been involved in a previous murder. "It is difficult not to conclude the coverage was designed to have the maximum impact possible," Mr Grieve told the court. "While not all details will ... be remembered, it is the overall impression that matters. The prejudice lies in the impression given of Mr Jefferies' character."

The Sun and Daily Mirror deny their reporting could have impeded or substantially prejudiced any future court proceedings. The court finished hearing evidence last night and the judges reserved judgment for a later date.