The Scottish appeal court has publicly identified a gangland supergrass whose identity is secret and protected by law.
The senior member of a significant organized crime organization served as the covert human intelligence source (CHIS).
Later, he testified in two murder cases that resulted in convictions.
Under the Contempt of Court Act of 1981, the High Court issued an order prohibiting the publication of his name or likeness last year.
However, the man was identified in an appeal court decision that was posted online on Tuesday along with a description of his hiring as a paid police informant.
After the BBC inquired as to whether the court order was still in effect, the judgment was removed.
The court was debating an appeal against Christopher Hughes' conviction for the slaying of Dutch crime blogger Martin Kok.
In December 2016, Kok, a convicted murderer, was shot and killed outside a sex club in the Netherlands.
Hughes belonged to a serious organized crime group that James and Barry Gillespie, who are thought to have died in Brazil while evading capture, were thought to have led.
The informant testified during Hughes' trial at the High Court in Glasgow last year. He was a part of the same organization that operated throughout Scotland and Europe.
Hughes was found guilty of engaging in what was referred to as a brutal "execution" that lured Kok to his death.
He was sentenced to life in prison last April and must serve at least 25 years before he can apply for parole.
The informant also testified for the prosecution during Jordan Owens' trial after he was found guilty of shooting a young father in Glasgow near a playground.
Jamie Lee was murdered in the city's Castlemilk in July 2017, and Owens was sentenced to at least 23 years in prison.
The appeal court's ruling, which was released on Tuesday, upheld Hughes' conviction for killing Kok.
It also explained how the police approached the informant in July 2016 and how he later became a CHIS after being paid thousands of pounds for information.
Before the BBC questioned its contents, the court opinion containing his name had been available online for several hours.
In the afternoon, it was taken down.
The opinion has been withdrawn, and we are investigating this as soon as possible, according to a spokesman for the Scottish Courts and Tribunal Service.