Prosecutors working on the Madeleine McCann case say they are fearful of charging prime suspect Christian Brueckner because of Germany's strict double-jeopardy laws.
For more than a year, prosecutors have been working closely at gathering enough evidence to charge German paedophile Brueckner with the murder of the 3-year-old back in 2007.
But the lead prosecutor Hans Wolters told the Mirror they have one shot at nailing Brueckner, saying if they fall short he will never again be able to be charged for crimes related to McCann.
"If we file charges and he is acquitted, then the case is dead forever," he told the Mirror.
"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."
Wolters explained this part of the reason why investigators are taking so long to gather evidence.
Mobile phone records place him in the Portuguese resort of Praia da Luz on the night Madeleine vanished in May 2007, a few days before her fourth birthday.
Controversy surrounding Germany's double jeopardy law reared its head after a taxi driver was acquitted of raping and killing a child, however years later after technological advances, his DNA was matched to a sperm sample at the scene.
Wolters told the Mirror it was clear the taxi driver was guilty, but he could not be charged again, describing it as "so tragic".
Meanwhile, Brueckner could be moved to a maximum security former Gestapo guillotine jail ahead of interrogation, it is reported.
The 43-year-old is serving a 21-month sentence on an unrelated drugs case at a prison in Kiel in northern Germany.
He will be transferred to a maximum security prison when that sentence ends in January and he serves out the rest of a seven-year term for raping a 72-year-old American woman in Praia da Luz, Portugal.
He could end up at the notorious Category A Wolfenbuttel prison, which the Nazis used to hang or behead Gestapo prisoners in gruesome executions.