What is contempt of court, and why can't the press report some trials?
Contempt of court covers conduct that interferes with the administration of justice — and reporting restrictions exist because a jury must decide on the evidence it hears in court, not on what it read beforehand.
The central concern. Jurors are ordinary people. If a newspaper publishes a defendant's previous convictions, a confession later ruled inadmissible, or simply asserts guilt, a fair trial may become impossible. The remedy — abandoning a trial and starting again — is enormously costly and traumatic for everyone, particularly complainants.
Strict liability contempt. Under the Contempt of Court Act 1981, a publication that creates a substantial risk of serious prejudice to active proceedings is contempt regardless of intent. You do not need to have meant to prejudice anything. Proceedings become active at arrest, the issue of a warrant, or charge — which is why detailed coverage stops abruptly once someone is arrested.
Why coverage before charge is fuller. Before proceedings are active, the strict liability rule does not apply — though defamation and privacy law still do, as several newspapers have discovered expensively.
Reporting restrictions are separate orders and include: automatic lifetime anonymity for complainants in sexual offence cases; restrictions protecting under-18s; postponement orders where several linked trials are to be held, so a jury in the second is not influenced by reporting of the first; and orders in the interests of national security or witness safety.
Family and Court of Protection proceedings are subject to their own restrictions, which is why reporting is limited and anonymised.
Other forms of contempt: disobeying a court order; interfering with witnesses or jurors; jurors researching the case online, which is a specific criminal offence and has resulted in imprisonment; taking photographs or recordings in court; and scandalising the court, now abolished as an offence in England and Wales.
Social media is the live problem. The rules apply to anyone publishing, including individuals. The Attorney General has pursued members of the public, and sharing an old news article about a defendant's past can itself be contempt.
General information, not legal advice.