What Does a Jury Do?

The division of labour is precise. The judge decides what the law is, what evidence the jury is allowed to hear, and how to instruct them. The jury decides what happened, based only on the evidence presented in court.

So a jury never rules on whether a law is fair or how it should be interpreted. It answers a factual question: given this evidence, are we satisfied that the defendant did what is alleged, to the required standard?

Jurors are selected at random from a broad pool, typically drawn from electoral or residence records. Randomness is the point, because a panel chosen by either side would defeat the purpose.

Selection then removes those who cannot serve fairly. People connected to the case, or with a direct interest in it, are excluded. Systems differ considerably in how much either side can challenge individual jurors, with some jurisdictions allowing extensive questioning and others very little.

Jurors deliberate in private with no outside contact about the case. Most systems ask first for unanimity and may accept a majority verdict after sufficient time has passed.

A few features are near universal:

• •Deliberations are secret, and jurors are not required to explain their reasoning
• •The burden of proof stays with the prosecution throughout
• •If jurors cannot agree, the result is a hung jury and a possible retrial
• •Jurors must decide only on evidence heard in court, not their own research

The historical argument is about placing a check between the state and the individual. A government can write laws and appoint judges but it cannot easily control twelve randomly selected citizens, and that has been seen as a safeguard against oppressive prosecution.

There is also a legitimacy argument. Verdicts reached by ordinary members of the community are often more readily accepted than decisions handed down by officials, particularly in contentious cases.

Juries are not universally admired. Critics point to the risk of bias, the difficulty of understanding complex financial or scientific evidence, and the fact that no reasons are given, which makes appeals harder.

Some countries use professional judges alone, or mixed panels of judges and lay members. Even in jury systems, the vast majority of criminal cases never reach a jury, being resolved by guilty pleas or heard in lower courts. The jury trial is emblematic but statistically rare.

A jury can acquit even when the evidence clearly establishes that the defendant did what is alleged, and because deliberations are secret and no reasons are given, nothing can be done about it. This is usually called jury nullification.

It is not a right that juries are told they have, and in most jurisdictions lawyers are not permitted to invite it. It has been used historically both admirably, in refusing to convict under laws seen as unjust, and appallingly, in refusing to convict defendants who harmed people the jury did not value. It is best understood as an unavoidable consequence of secret deliberation rather than a designed feature.

The independence of juries was hard won. In 1670, the Quaker William Penn was tried in London after preaching to a crowd in the street. The jury refused to convict, and the judge responded by fining the jurors and locking them up. One juror, Edward Bushell, challenged his imprisonment, and the court ruled that jurors could not be punished for their verdict. That decision, known as Bushell's Case, is the root of the modern rule that a judge cannot overturn an acquittal or penalise a jury for reaching a conclusion the court dislikes.

Secrecy creates a puzzle for anyone who wants to know how juries actually decide. In England and Wales, for example, it is a criminal offence for jurors to reveal what was said in the jury room. Researchers therefore rely on indirect methods. They run mock juries who watch a recorded or simulated trial and deliberate on camera, interview real jurors about their general experience without asking about deliberations, and compare actual verdicts with what the trial judge would have decided. Studies of that last kind have found that judges and juries agree in most cases.

Not every jury decides guilt. In the United States, serious federal charges normally require an indictment from a grand jury, a larger panel of citizens, between sixteen and twenty-three at federal level, that meets in secret to hear the prosecution's evidence. It decides only whether there is enough evidence to put someone on trial, not whether they are guilty, and the defence usually does not present a case. England, where the grand jury originated, largely abolished it in 1933, leaving the decision to charge with prosecutors and magistrates.

The twelve-person trial jury is a strong tradition rather than a universal rule. Scottish criminal juries have fifteen members, and some American states use smaller juries for minor cases. Rules on agreement vary too. England and Wales have allowed majority verdicts, such as ten jurors to two, since 1967, mainly to reduce the risk of a single juror being bribed or intimidated into blocking a verdict. In the United States, the Supreme Court ruled in Ramos v Louisiana in 2020 that juries must be unanimous to convict anyone of a serious crime in state courts.

Most talk about juries concerns criminal trials, but the civil side differs sharply between countries. The Seventh Amendment to the United States Constitution preserves the right to a jury in many federal civil cases, and American juries routinely decide not only who was at fault in a lawsuit but how much money should be paid. That is why the United States produces headline damages awards, some of which judges later reduce because they are out of proportion to the harm or exceed limits set by law.

England and Wales went the other way. Civil juries there have become rare, and most civil disputes are decided by a judge sitting alone. A jury remains possible in a few kinds of case, such as claims of malicious prosecution or false imprisonment, often brought against the police, where a panel of citizens is seen as a valuable check on authority. Defamation cases were long a major exception, but since 2013 they have normally been tried by a judge alone too. In much of continental Europe, civil cases are decided without juries at all.

Many countries involve ordinary citizens in criminal trials without using a separate jury. In Germany, lay judges called Schöffen sit on the bench alongside professional judges in many criminal cases, hearing the evidence, deliberating together and voting on both guilt and sentence. Their vote carries the same weight as a professional judge's. The arrangement keeps a lay voice in the courtroom while letting judges explain the law during the deliberation itself, rather than through instructions given beforehand, and the court gives written reasons for its decision, which makes any appeal more straightforward than after an unexplained jury verdict.

Japan offers a more recent example. It experimented with juries between 1928 and 1943, then relied on professional judges for decades before introducing the saiban-in, or lay judge, system in 2009. For serious crimes such as murder, six randomly chosen citizens sit with three professional judges, and together they decide both guilt and sentence. A guilty verdict needs a majority that includes at least one professional judge and at least one citizen. Supporters hoped the reform would make justice more open and easier for the public to understand. Participants must keep the content of deliberations secret for life, a duty some have described as a heavy burden.

A jury decides questions of fact using only the evidence presented, while the judge decides the law and the sentence, and the system exists mainly as a check on state power in the hands of ordinary citizens.