Journalists have to be especially careful when they are writing about court cases and crimes.
Their reports are read, seen or heard by lots of people, including the 12 ordinary men and women (15 in Scotland) who form the jury.
It is the jury's job to look at all the evidence in a court case and decide whether the accused person is innocent or guilty of committing a serious crime.
What if their decision was influenced by what they saw on the television, or read in a newspaper? It wouldn't be a fair trial!
That's why there is a law called the Contempt of Court Act 1981 to stop journalists reporting information that could affect the outcome of a court case.
What kind of things might influence a jury?
Reporting that an accused person has broken the law before. Usually the jury is not told about this, so they can make a decision based purely on current evidence.
Calling the accused person "a burglar" for example, before the jury have decided whether he is innocent or guilty.
Photographs may influence a jury. In Scotland, pictures of an accused person are hardly ever allowed to be used.
The general rule is: A journalist who knows more than the jury should keep it to themselves.
What can you report without falling foul of the contempt law?
Once someone has been arrested, and before the court case, reports should not give much more than the person's:
Once the trial has started, you are allowed to report what happens in court. There are special press benches where journalists sit and make accurate notes about what people say.
- the crime for which they have been arrested e.g. burglary
In most cases where children under 18 are involved (17 in Northern Ireland), you can't report anything that identifies them e.g. their name, age, address.
Judges also have the power to ban journalists from publishing certain details about people involved in the court case.
What happens if a journalist is found to be in contempt of court?
If the judge decides the accused person won't get a fair trial, they might release them. This could mean letting a criminal off or stopping an innocent person from clearing their name.
The newspaper or broadcaster may face a huge fine, or even prison.
The Sunday Mirror had to pay £175,000 for printing information which could have affected the trial of Leeds United footballers Jonathan Woodgate and Lee Bowyer. And the whole court case had to be re-run.
Why have a law about contempt?
It's there to strike a balance between:
A person's right to be treated fairly in court
A journalist's right to report what is happening in the world