Double jeopardy is an ancient legal principle that has been around for hundreds of years and is still in use today. It states that if you have been tried with a crime and a verdict has been reached¹ (guilty or not guilty - ie, convicted or acquitted), then you may not be tried again for the same crime. Once you have had your trial, that’s it. Both parties in the trial must abide by the verdict or else appeal, and the prosecution cannot decide to re-prosecute the person and run the trial again. This law is in effect in many countries including Australia, the United Kingdom² and the United States (where it is a constitutional right). It has also been the subject of many thriller movies, such as the inventively-titled Double Jeopardy.

For example, if Sam is acquitted in court of the murder of Frank, she cannot be brought to court again at a later stage for Frank's murder. However, this does not apply to other murders Sam may have committed — Sam cannot be re-tried for the murder of Frank, but she may be tried for the murder of another, completely different person. So if Sam murders Fred as well, she can indeed be tried for the second murder.

Benefits of Double Jeopardy

The major benefit of double jeopardy is that it stops people from being put on trial again and again for the same crime. This means that the accused does not have to go through the strain and stress of trial after trial after a verdict has already been reached. It also means that the prosecution (in a criminal trial that would be the state or the police) cannot continually try to convict somebody of a crime. Double jeopardy also means that individuals won't be brought to trial on little or no evidence. If police bring a weak, half-formed case with no evidence to court, the accused may be acquitted and the police are not permitted to prosecute them again. Because of this, people are rarely prosecuted unless there is sufficient incriminating evidence.

Disadvantages of Double Jeopardy

Double jeopardy can cause tremendous problems for the prosecution. They must always be very sure about their case before they begin; essentially they get only one shot at successfully prosecuting the accused person. If the police are almost certain somebody committed a crime, but are lacking the ultimate piece of evidence, they may waste valuable time trying to gather more evidence to incriminate the person. In the meantime, the person could either commit more crimes, or leave the country, or both before their case comes to court³.

Also, in most cases, double jeopardy still holds even if new evidence is uncovered. This has caused tremendous problems in a number of cases, where there has been plenty of evidence against a person, but not quite enough to convict them. In several cases people have been acquitted of murder — just because some evidence was not quite good enough — only to find that 20 years later new forensic technology has led to incriminating evidence against them, yet they cannot be tried! Specific cases where this has happened has lead to successful and unsuccessful calls to modify the double jeopardy laws to allow a person to be tried again if sufficiently important new evidence is discovered.

More from the Edited Guide

• Who Does What in the English and Welsh Legal System
• The High Court of Australia and Constitutional Interpretation
• Insanity and The Law
• DNA Fingerprinting
• Rumpole's Golden Thread

Related BBC Links

• For a look at an instance where the prinicple of double jeopardy may have allowed guilty persons to go free, see the BBC's report on the murder of Stephen Lawrence.

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¹ A second trial usually can be held after a mistrial, because in mistrials the trial is not complete and there is no verdict.
² In the United Kingdom, however, retrials are now allowed if there is 'new and compelling evidence'.
³ In cases where a particularly egregious crime has been committed, or if the accused person is deemed likely to flee, he or she may be 'held without bail' - that is, jailed until the trial.