A Worcester judge ordered three men to be handcuffed in the dock after fears of an escape plot.
Adam Mole, Mark Reece and Peter Bennett were on trial for a vicious attack on convicted drug dealer Michael Coffey.
Judge Andrew Geddes said staff from a security firm bringing the trio to Worcester Crown Court had overheard talk in a prison van that someone was going to help them escape.
The jury was not told about the scare and were unable to see the handcuffs.
The Kidderminster trio were unanimously convicted of causing Mr Coffey grievous bodily harm with intent.
Mole, aged 25, of Hurcott Road; Mark Reece, 25, of Queen Street; and Peter Bennett, 31, of Jubilee Drive, were remanded in custody for reports.
Mr Coffey was set upon in Kidderminster and beaten unconscious, suffering a collapsed lung and broken teeth.
The attack was witnessed by Shaun Stanton, who ruled out a claim by the attackers that Mr Coffey was carrying a knife and that they acted in self-defence.
Adam Western, representing Mole, said that his client feared Mr Coffey, who had a formidable reputation for violence.
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