The 43-year-old German national is currently in prison on drug trafficking charges but will be released in January. Prosecutors fear he will vanish if his appeal is upheld.
The prime suspect in the disappearance of British girl Madeleine McCann has had an appeal rejected by Europe's highest court.
Christian B, who was identified as a suspect in the McCann case in June, challenged the issuing of a European Arrest Warrant (EAW) that saw him extradited from Italy to Germany over the rape of a woman in Portugal in 2005.
He was later convicted of raping the 72-year-old American woman in Praia de Luz, the same resort McCann, three, was staying in with her family when she vanished on May 3, 2007.
Christian B, a 43-year-old German national, took his appeal to the European Court of Justice (ECJ), arguing he had been unlawfully extradited under the warrant in 2018.
Christian B, whose full name is protected for legal reasons, tested the validity of the EAW in the courts because it was issued for drugs charges, not the 2005 rape.
According to EAW rules, it is not possible to be tried for a different charge to the one the suspect has been arrested and extradited for.
But in its preliminary opinion, the ECJ noted that the consent of the Italian authorities was all that was needed for German prosecutors to pursue an additional case against Christian B for the rape in Portugal.
The ECJ's guidance is not legally binding on the German court, which is yet to make a ruling in Christian B's appeal.
Christian B is currently serving a 21-month sentence for drug trafficking in a high-security prison north of Kiel, Germany, and is due for release in January.
Prosecutors fear he will disappear if he is released as scheduled.
He was convicted of rape in December 2019 and handed a seven-and-a-half-year sentence. If his appeal in the rape trial is quashed in German courts, he will remain in prison until 2027.
McCann has never been found and the case became of the most infamous missing person investigations in recent history.
Described as a drifter, Christian B was known to frequently travel between Germany and Portugal and lived on the Algarve coast near the rented apartment the McCanns were staying at the time the girl went missing.
German prosecutors say they believe he killed her.
Christian B's appeal is ongoing.
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