It was once something of a common fallacy that juries got to hear every piece of evidence before reaching their verdict. Now, in increasingly startling circumstances, we know that routinely they do not. What they hear is the product of pre-trial hearings as the prosecution and the defence seek to tilt the balance of the pending courtroom proceedings in their favour. What jurors are told, and what they are not, can have a strong influence on their thinking. In that light, it is relatively unsurprising that two juries considering the case of David Bain arrived at different conclusions. And when material withheld from a jury is later made public, it is totally unsurprising that there will be widespread unease.

The Bain trials encapsulate the issue. The first jury did not hear evidence that suggested Laniet Bain was about to reveal her incestuous relationship with her father, providing a motive for him. The second, it now transpires, did not hear police claims that David Bain had said "I shot the prick" in his 111 call to report the deaths of his family. The High Court and the Court of Appeal turned down defence applications for the evidence to be suppressed, but the Supreme Court upheld the application and it was not revealed to the jury. Also suppressed from the retrial jury was Crown evidence that Mr Bain had told a school friend of a plan, in the words of the appeal court, to rape a female jogger, using his paper round as an alibi.

Other high-profile trials have been similarly afflicted. Two years ago, in the Louise Nicholas case, a suppression order prevented the High Court jury from hearing that two of the accused were in jail for the kidnap and rape of a young woman. There was considerable, and justifiable, disbelief when this became public knowledge after not-guilty verdicts.

The Supreme Court and the Court of Appeal have taken the right step in releasing the material withheld from the Bain retrial jury. The outcome is that it could be argued the public are now in a position to make a better judgment about Mr Bain than either of the two juries. Such are the distortions that arise when legal counsel, at the behest of our adversarial system of justice, set about gaining a courtroom advantage. All too often, the result is a justice system in a bind, as the progression of the 111 call evidence through the courts attests.

The courts' willingness to suppress certain evidence suggests an implicit mistrust of jury members' acumen. Yet there is an essential contradiction in this approach. Juries are entrusted to assess a large amount of evidence about often complex or technical issues. Often, as in the 12-week sitting of the Bain retrial, this will involve dissecting the widely differing views of forensic and pathology experts. But the jury was not allowed to hear the school friend's allegation of a "rape" plan because the Court of Appeal ruled it was too prejudicial against Mr Bain. Likewise, that jury was not trusted to assess the 111 call.

Chief Justice Sian Elias said the Supreme Court had not considered this evidence to be relevant or reliable. It wanted to ensure Mr Bain had a fair trial. To underscore how tricky this balancing is, the "relevant or reliable" test was the one that suppressed the defence's incest evidence in the original trial.

After the retrial verdict, Chief Justice Elias said it would be "an extraordinary step" for the court to now keep its reasons for making any decision secret. She is right about that, but the consequence of a jury not fully in the picture is a public making its own judgment. Heavy lashings of suppression have produced a strong dose of distortion. Far better that juries hear every scrap of evidence and be trusted to reach the right decision.