Kerim Kurt promised to tell the truth whilst holding the New Testament and not the Koran as he gave evidence in a robbery trial.
The jury at Liverpool Crown Court was discharged after the judge, Patrick Thompson, realised Mr Kurt's faith during cross examination.
It's thought the man had agreed to swear on the Bible because he had respect for all holy books.
The man chose to use the Bible so he could conform to traditions in Britain, it's claimed.
Recorder Patrick Thompson told the BBC he accepted his error and that the case should have proceeded.
"Mr Kurt had been asked by the court staff, prior to giving evidence, whether he was content to take the oath on the New Testament and he confirmed that he was.
"This was because Mr Kurt had declared that he respected all holy books and wanted to swear on the holy book of the country in which he was residing."
He said he "took the view that Mr Kurt should have sworn on the Koran as a Muslim".
"However, in hindsight, it is a personal matter for any witness as to how they wish to be sworn and having been given the option, Mr Kurt chose to be sworn on the New Testament."
A new trial will start on 27 April.