Speaking exclusively to The Mirror, chief prosecutor Hans Christian Wolters said: “If we file charges and he is acquitted, then the case is dead for ever.
“In Germany , once you have been acquitted, you cannot be charged again, at least only in very exceptional cases.
“If we now are hasty and he was acquitted because the court said ‘Ah, we still have a few doubts’ then we would not be able to get him later.”
Speaking from the public prosecution office in Braunschweig, Lower Saxony, Mr Wolters added: “Therefore we want to collect as much evidence as possible.”
Madeleine McCann disappeared in Praia da Luz, Portugal on May 3, 2007
Paedophile Brueckner, 43, was named as the prosecution’s prime suspect in the Madeleine case, which Germany is treating as a murder investigation.
A case in Bremen illustrated how rigid the German double-jeopardy law can be.
Mr Wolters said: “Here it was completely clear that this taxi driver was the perpetrator, but it was not possible to charge him again… so tragic.”
Brueckner is currently in jail serving a 21-month sentence for drug-running.
Hans Christian Wolters said German prosecutors are wary of charging the suspect
It ends in January 2021 but he has already been sentenced to seven years for raping a pensioner in Praia da Luz.
He is appealing this conviction.
The UK had a double-jeopardy law until 2005.
The next year Billy Dunlop, acquitted of murdering a pizza deliverer, was convicted following his confession.