Two court dock officers were hauled before a judge after police overheard them talking to drugs boss Aram Sheibani about his case during his trial.
Sheibani would later be jailed for 37 years, after being convicted of being involved in an international cocaine conspiracy which funded a lavish lifestyle.
On one day of his 10 week trial, custody officers Samantha Dennis and Steven Lewis were overheard speaking to Sheibani about his case during a break.
READ MORE: The secrets an international cocaine dealer is taking to prison with him
Manchester Crown Court heard that Ms Dennis told him: "Only answer or agree to the stuff that has been agreed."
While Mr Lewis said: "This is what the prosecution is like, this is what they do."
Sheibani was giving evidence when the comments were made on May 28.
Prosecutor Nick Clarke QC claimed it 'changed the manner of (Sheibani's) answers' under questioning, and he answered some by saying 'I can't remember' or 'if that is what was agreed'.
The trial continued and Sheibani was later convicted.
The comments were reported by a police analyst who was listening to proceedings via video link.
Due to coronavirus restrictions, video links were set up to allow others unable to attend in court physically to follow the trial.
Defendants are told they must not speak to anyone about their case while they give evidence, including their legal team.
Judge Anthony Cross QC said it was a 'serious matter' but said no further action would be taken against the officers, who were not prosecuted.
He ordered that GEOAmey, the company responsible for escorting prisoners to courts, install signs saying that 'staff must not speak to any detained person about their case'.
GEOAmey said the issue was already part of their training, but the judge said he wondered 'quite how often that training was revisited'.
The judge said it is 'essential' that staff have a 'good relationship' with prisoners.
He said: "It is wrong to say they should not speak, but there is a line that must not be crossed.
"That line is no talk about the case at all."
The judge described Ms Dennis, who had 16 years experience, as a 'co-operative, industrious and valuable servant of the court'.
"It was with great surprise that I found out she was involved with something like this," he said.
"Mr Lewis I know less well because I have seen him less frequently."
The court was told they are 'extremely embarrassed, chastened and regretful about what went on'.
Ms Dennis has since resigned her position while Mr Lewis is off work with stress, the court heard.
