Criminals are escaping justice because of a lack of organisation within the Crown Prosecution Service (CPS), a judge has said.
Judge Aidan Marron QC said jurors acquitted defendants in at least two cases where they should have been convicted because they lost patience.
His criticism came during a trial at Blackfriars Crown Court in London on 5 March.
The judge's comments can only now be reported for legal reasons.
He was speaking after publicly chastising prosecutors for putting a map that was difficult to read in front of jurors and for not arranging witnesses to appear in court at the right time.
Explaining that the case was being adjourned to allow the prosecution time to get witnesses to court, the judge said: "It's not satisfactory but perhaps the less said at this stage the better."
Once the jury had left the courtroom, he said: "This is the third out of four trials where witnesses just haven't been arranged."
"The result was in two other cases there were acquittals when really there should have been convictions because the jury had just had enough.
"The CPS are just going to have to learn to get things organised better."
Earlier, the court heard that a prosecution witness had only been contacted 24 hours before he was de to appear in court and had not been able to attend at such short notice.
In the same case, as prosecutor James Lachkovic was explaining a small, detailed map to the jury, the judge told him: "It's a complete muddle. It's a complete, unadulterated, unmitigated muddle."
Judge Marron's comments came after the trial of man accused of unlawful and malicious wounding.
In response to the judge's comments, a CPS spokesman said: "It is regrettable that we could not arrange for the witnesses to appear on schedule in this case.
"We are taking steps to help ensure it does not happen again."