IN 1954 an Ohio jury was told it must acquit Sam Sheppard of murdering his wife if the jurors had a “reasonable doubt” that he had done so. The judge then defined “reasonable doubt”:

It is not a mere possible doubt, because everything relating to human affairs or depending upon moral evidence is open to some possible or imaginary doubt. It is that state of the case which, after the entire comparison and consideration of all the evidence, leaves the minds of the jurors in that condition that they cannot say they feel an abiding conviction to a moral certainty of the truth of the charge.

Sheppard was convicted. Larry Solan of Brooklyn Law School reckons that this and other baffling instructions misled the jury into thinking that the burden of proof was on Sheppard to prove himself innocent, not on the state to prove him guilty beyond a reasonable doubt. In a second trial, in 1966, he was found not guilty and freed.

A jury is a buffer between defendants and the might of the state, and a jury trial is guaranteed in America’s bill of rights. But there is reason to worry that juries often do not understand what they are told to do to fulfil this role. Jurors are not (usually) lawyers, which is the point. They are the defendant’s peers. But their instructions are written by lawyers, who areoften so immersed in their professional argot that they do not realise how impenetrable it can be to outsiders.

Take this sentence from Massachusetts’s civil-jury instructions: “A preponderance of the evidence is such evidence which, when considered and compared with any opposed to it, has more convincing force and produces in your minds a belief that what is sought to be proved is more probably true than not true.” The sentence is not only long; the bigger problem is that it has four clauses, embedded within one another. This kind of prose is hard to process, especially for non-native speakers, even more so when it is spoken rather than written down.

Another problem is the passive voice. Though the passive has some applications, it is overused in formal contexts. Like convoluted clauses, passive jury instructions can be hard to follow. Research has shown that when people hear sentences such as “the woman was visited by the man”, and are quickly prompted to identify who was the “do-er” and who “acted upon”, their reaction time and accuracy are considerably worse than when hearing the active-voice equivalent.

A final problem is legalese. Lawyers love words such as “notwithstanding” and “inference”, but studies suggest as many as half of jurors think “preponderance” has something to do with pondering. Even plain words like “burden” have specialised meanings in court.

Janet Randall, a psycholinguist at Northeastern University, has found that rendering these instructions in plain English, stripping out passives and legalese especially, makes them much easier to interpret. Providing a written version brought an even bigger benefit. She first recorded modest results when testing psychologists’ favourite lab rats—their students. But these are people who did well on English tests to get into university. When she recruited respondents online, who looked more like the actual jury pool overall, the good effects of the plain-English instructions shot up.

The Supreme Court has weighed in on ambiguous jury instructions, but has not yet struck down those that are merely hard to comprehend. Some American states have adopted simplified language, and some provide each juror with written instructions. But some still have not. A justifiable reason is that it can be difficult to render legalese accurately into terms that sound like conversational English. Less defensible reasons are mere inertia or, even worse, the belief on the part of a few judges that cumbersome formal language is needed to give jurors a sense of the majesty of the law.

Jurors will not often want to admit they don’t understand. They are eager to end the trials and get back to their lives, and lawyers and judges in crowded court systems want them to get on with it, too. But bafflement should worry anyone who may face a jury, particularly in a country where the state can execute a defendant (see article). As long as that is the law in America, every easy reform that makes the system work better should be seized with urgency. Cleaning up the language of courtrooms is an obvious place to start.