Lawyers representing the German paedophile suspected of abducting Madeleine McCann say that a key prosecution witness is a criminal who swapped information for police favours.
Christian Brückner, 43, is alleged to have told a friend he “knew all about” what happened to Madeleine while out drinking in a bar in 2017.
It is also alleged he even showed the man a video of him raping a woman. The friend called the police and the tip-off is said to have sparked the police interest in Brückner as their chief suspect in the Madeleine case.
But now, Friedrich Fülscher, a lawyer representing Brückner, says that the informant may later, in return, have got early release from a sentence he was serving in a foreign country.
"If this is the same person, I think it's the worst witness you can get,” Mr Fülscher told Sky News.
“A human who has spent his whole life cheating people for his own benefit is never a reliable witness."
Last month, Hans Christian Wolters, the Braunschweig state prosecutor leading the investigation said people have to be realistic about the prospect that it “could be stopped” and charges may never be brought against Brückner.
“I am currently unable to predict the outcome of our investigation but we are still convinced of the guilt of the accused and hope for further promising investigative approaches,” he said.
But Mr Fülscher said this would not be good enough.
"If you pee in the same place long enough it will stink,” he said.
“And that's definitely what's happening in the Christian B case. He won't be able to lead a normal life at any point, without being recognised and facing hostility.
"A prosecutor who goes public (during an investigation) knows that. He can destroy a reputation and it was taken very lightly in this case."
Earlier this month, police in Germany swooped on an allotment just outside Hamburg where they found a cellar reportedly built by Brückner.
Locals said Brückner had stayed in the area in 2007, the year in which three-year-old Madeleine went missing from Praia da Luz in Portugal.
Brückner remains in prison in Kiel, northern Germany on drugs charges and is awaiting the result of an appeal to overturn a rape conviction.
He was convicted last year of attacking a 72-year-old American tourist in Praia da Luz in 2005, but has argued at the ECJ that he had been extradited to Germany from Portugal, and later Italy, on a different charge.
According to European arrest warrant rules he should not have been able to have been subsequently put on trial for a separate crime, his lawyers said.