There must have been sighs of relief at the Ministry of Justice last week when officials realised that they would not be required to abolish trial by jury. The threat this time was not from the department’s grandly titled Commissioner for Victims and Witnesses. Louise Casey’s absurd demand this month that defendants facing potentially career-destroying charges of dishonesty should lose the safeguards associated with our most cherished mode of trial has rightly received no serious support.

Instead, what might have forced the government’s hand was the European Court of Human Rights. The Strasbourg judges upheld a claim against Belgium by Richard Taxquet, a former political aide sentenced to 20 years in 2004 for assassinating the former Belgian deputy prime minister André Cools in 1991.

Taxquet claimed that his right to a fair hearing under article 6 of the human rights convention had been breached because the jury that convicted him in Belgium had given no reasons for its decision. Although jurors had been asked a series of questions by the court, Taxquet could not tell from their one-word answers why he had been convicted of premeditated murder rather than a less serious homicide.

Fearing that success for Taxquet at Strasbourg might require all trial courts in Europe to give reasoned judgments, the British government lodged written submissions in support of Belgium. In the government’s view, a British jury did not need to give reasons because its verdict followed a detailed summing-up by the judge. The Irish government added that trial by jury enjoyed widespread public support and had been around for centuries before the human rights convention. Even France warned the Strasbourg court to leave well alone.

Finding a breach of Taxquet’s right to a fair trial, the judges said he had not been given ‘sufficient safeguards enabling him to understand why he was found guilty’. Belgium was ordered to pay him €4,000 in damages – which may not be worth very much when he comes out of prison.

But the human rights judges insisted they were not calling into question the lawfulness of lay juries deliberating without professional judges. Traditional juries of this kind, they noted, could be found in 10 of the 47 states that have signed the human rights convention.

‘The convention does not require jurors to give reasons for their decision and ... article 6 does not preclude a defendant from being tried by a lay jury even where reasons are not given for the verdict,’ the court said. ‘Nevertheless, for the requirements of a fair trial to be satisfied, the accused, and indeed the public, must be able to understand the verdict that has been given; this is a vital safeguard against arbitrariness.’

On the day the Taxquet judgment came out, the lord chief justice of England and Wales was due to deliver the Judicial Studies Board lecture in Northern Ireland – where they know a thing or two about reasoned verdicts. After a quick read of the Strasbourg judgment on the plane to Belfast, Lord Judge offered his colleagues some instant analysis.

From the UK’s point of view, he explained, the critical feature of the Belgian trial process was the absence of a judicial summing-up. ‘What seems to me to be clear from the judgment,’ Judge said, ‘is that a properly structured summing-up followed by a verdict of the jury ... provides an ample understanding to the defendant, and to the public, of the reasons why the jury decided that the case against the defendant has been proved.’

But Judge – a staunch defender of the jury system because of its protection against potentially oppressive and unjust criminal laws – foresees other, more subtle, threats to jury trial.

The first is that children are no longer being taught to listen and think simultaneously, an essential requirement for every juror. Of course, courts can make more evidence available on screens to those more used to absorbing information in this way. But that would not enable jurors to decide which of two conflicting witnesses was telling the truth.

The second threat to the jury system is that jurors are increasingly looking on-line for information about cases they are trying. This, suggested the lord chief justice, might amount to a criminal contempt of court for which jurors might be punished.

Judge gave the example of a trial more than three years ago. One of the jurors had seen a reference to a defendant on a BBC news website. This led the juror to inform his fellow members that the defendant had a prior conviction for money laundering. In fact, the defendant had pleaded guilty to a different offence. The Court of Appeal ordered a retrial. But if another juror had not decided to ask the judge why they had heard nothing about the defendant’s convictions, the matter would never have come to light.

Then there is Twitter. The social network could thwart even a retrial, Judge explained. It was possible for someone to send a prejudicial tweet from a courtroom during a trial that could be retrieved by a mischievous juror during a second trial.

And yet he had to admit that there was no statutory prohibition on tweeting in court. The same applied to emails, although that message does not seem to have got through to the usher who asked me to stop using my BlackBerry in the High Court last week. We cannot stop people tweeting, the lord chief justice concluded, but if jurors looked at prejudicial tweets there would be a very serious risk to the fairness of a trial.