Christian B, as he is known under privacy laws, had denied three rapes and the sex abuse of two young girls while he was living on the Algarve coast.

During a trial that began in February, chief prosecutor Ute Lindemann branded the German drifter a "sadistic psychopath" and urged the judge to jail him for 15 years.

She also said he was so dangerous - with previous convictions for rape, child sex abuse, theft and fraud - he should be held in preventive detention after serving his sentence.

But his own lawyer said he was put on trial for the sex crimes this year only because he was the suspect for the abduction of Madeleine, who vanished from her family's rented holiday apartment in Portugal in 2007.

In his closing speech this week, defence lawyer Friedrich Fulscher said: "This story will teach us what terrible consequences it can have when the investigating officers of the public prosecutor's office lose the necessary emotional distance from a case, and this attitude is combined disastrously with amateur investigations by a police authority."

He said Christian B should never have been charged with the sex crimes.

Addressing the prosecutor directly, he added: "Your decision (to prosecute) would have been different if the accused had not been Christian B, the man to whom you also want to attribute an offence which has attracted the attention of the world public and which lay like a fog over these proceedings."

Mr Fulscher had said at the start of the trial that the McCann investigation should not influence this case.

But several prosecution witnesses referred to it and Christian B's former friend Helge Busching claimed the defendant had confessed to him that he had abducted Madeleine.

Christian B, who moved between his native Germany and Portugal from the 1990s until his arrest and deportation in 2017, has been the main suspect for Madeleine's disappearance for at least seven years.

Hans Christian Wolters, the German prosecutor in charge of the Madeleine investigation, said he would appeal against the verdict to the German Supreme Court, saying he believed the judge was biased from the start.

He also repeated what he has said in the past, that he believes Christian B abducted Madeleine and that she is dead.

"This acquittal has no bearing on the Madeleine case," Mr Wolters said.

"Our investigation continues and we will see what happens. There is no forensic evidence yet, but I am not under any time or financial restriction."

Christian B, who is currently serving a seven-year sentence for the rape of an elderly American woman in Portugal, has not been charged over Madeleine and denies any involvement in her disappearance.

Read more:
Madeleine suspect's lawyer accuses 'biased prosecutors'
Christian B 'boasted of Portugal abduction'

The current trial in Braunschweig, Lower Saxony, has been held on intermittent days over the past eight months.

The main charge against Christian B was the rape of Irish holiday worker Hazel Behan in her room in the resort of Praia da Rocha in 2005. She has waived her right to anonymity.

Ms Behan was raped several times and whipped by a masked intruder brandishing a knife, in a prolonged ordeal that bore similar horrific hallmarks to the rape for which Christian B is in jail now, said the prosecutor.

But his lawyer said Ms Behan's description of her attacker did not match Christian B's, particularly a cross-like mark she said she saw on his right thigh, which he says he does not have.

Ms Behan's belief that Christian B was her attacker may have sprung from the influence of media reports about his rape conviction, said Mr Fulscher.

He accused two main prosecution witnesses, Mr Busching and Manfred Seyferth, of lying about video tapes they claimed to have seen allegedly showing Christian B raping an elderly woman and a girl of about 14 in his rented home in Portugal. The video tapes didn't exist, he said.

Judge Ute Engemann concluded there was not enough evidence to convict Christian B.

She also said Mr Busching had been inconsistent in his evidence in relation to the claims he made about seeing video tapes of offences committed by the defendant.

"He lied when he felt it was in his interests," Ms Engemann said.

Christian B was also charged with grabbing the wrist of a 10-year-old girl and exposing himself to her on an Algarve beach and masturbating in front of another young girl during a festival in a hillside village above the coast.

The five alleged sex crimes were said to have been committed between 2000 and 2017.

With this trial over, the Braunschweig prosecutor's office will be under pressure to refocus on its Madeleine investigation and decide whether to charge Christian B over her disappearance.