Madeleine McCann prime suspect Christian Brueckner is said to be fighting to be released early from prison and for £200,000 in damages.
The paedophile was cleared this week of his 2019 conviction for raping an American woman in the Algarve, Portugal.
Prosecutors for Madeleine have said they have evidence on the convicted rapist - but admitted the clock is now ticking to bring charges after he was found not guilty on five different counts of sex crimes on Tuesday.
Brueckner is currently scheduled to be released in September 2025, but the German is planning an appeal against the conviction keeping him behind bars.
A legal source reportedly told the Sun that although an appeal would take time, there was a possibility that Brueckner would be released sooner.
Madeleine McCann suspect Christian Brueckner arrives in court in Braunschweig, Germany on Tuesday, when he was cleared of five count of rape
Madeleine prosecutors say they have evidence on Brueckner, but admit time is running out to bring charges against the German
Kate and Gerry McCann were named as suspects in their daughters disappearance in September 2007 - four months after she went missing
Brueckner’s lawyer said in court he did not believe the 2019 conviction was safe and after a witness was discredited, the insider said.
They added that an early end to his sentence would give Brueckner ammunition to apply for compensation.
Brueckner had been accused of three rapes and two child sex abuse cases between 2000 and 2017 in Portugal, close to the resort where Madeleine vanished.
He has denied any involvement in the 2007 disappearance of three-year-old Madeleine in Praia da Luz, Portugal and has yet to be charged in relation to the incident, despite being identified as a key suspect in 2020.
In one of the rape cases, Brueckner of entering the holiday apartment of a woman aged between 70 and 80, tying her up and beating and sexually assaulting her.
He was also charged with entering a young Irish womans apartment via her balcony while she was sleeping, threatening her with a knife and raping her several times.
In another case he was alleged to have exposed himself in front of a 10-year-old German girl on a beach and to an 11-year-old Portuguese girl at a playground.
But Brueckners legal team raised concerns that cases against him were based on testimony rather than forensic evidence.
His main lawyer, Friedrich Fuelscher, suggested the German was only on trial because of his links to the Madeleine case, during his closing remarks at the courthouse in Braunschweig on Tuesday.
Wrongly imprisoned inmates in Germany can be awarded as much as £63 per day in jail.
It comes as Brueckners lawyers also took a cruel dig at Madeleines parents as a member of his defence team suggested the outcome of the trial would be very interesting for those who believe the toddlers parents were involved in her abduction.
Brueckner was accused of three counts of rape and two counts of child sex abuse allegedly committed in Portugal between 2000 and 2017
A lawyer acting for Brueckner said on Monday that the trials outcome would be very interesting for those that believe the toddlers parents were involved in her abduction. Pictured: The McCanns holding a poster in 2012
Madeleine McCann (pictured) went missing on May 3, 2007 from a Portuguese resort near Praia da Luz at the age of just three
Philipp Marquardt said: I think in the UK there are still quite a lot of people who think that the parents were involved in the Maddie case so from this point of view I think todays verdict will be very interesting for them.
The focus on Madeleines parents came after forensic examinations revealed traces of the three-year-olds blood in a car they rented 25 days after their daughters disappearance.
Mother Kate McCann told detectives there was no way Madeleines blood could have been found inside the car and continued to protest her innocence.
The parents were named as suspects in 2007 - four months after Madeleine disappeared. Their suspect status was lifted in 2008.