Scotland Yard has been urged to retest DNA samples ruled "inconclusive" in the hunt for Madeleine McCann .
Ex- detective Colin Sutton - who caught serial killer Levi Bellfield - says the move could be "a real game changer" in the investigation.
Colin Sutton reckons advanced testing methods could be applied to swabs taken from the holiday home in Praia da Luz, where Madeleine went missing in 2007.
Speaking on the Nine News Maddie podcast, the veteran detective - who solved more than 30 murders in his long career - was asked what it would mean if new tests revealed the presence of her DNA in the family's rental car.
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He said: "On that basis, that that car was hired by the McCanns three weeks after Madeleine disappeared, then it is a real game changer, isn't it?
“Because there is no way, according to information that we have, that she could have been in that car.
"The big question then is how can her DNA get into that car three weeks after she disappeared?"
Forensics expert Dr Mark Perlin has volunteered to analyse the samples taken from the holiday home and flat after it's claimed a specialist sniffer dog detected the "scent of death", The Sun reports.
The swab referred to was taken from the boot of a Renault Scenic hired 25 days after Madeleine went missing.
It was one of 18 ruled inconclusive 12 years ago.
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De Perlin believes that Pittsburgh lab Cybergenetis could unlock vital information.
The lab routinely unlocks complex samples and helped identify 9/11 victims.
He explained to the podcast: "If a lab can produce informative data, even if it is complex and mixed, but they can't interpret it then you can have tremendous injustice - of guilty people not being convicted, or innocent people staying in prison.
"What is needed is an objective and accurate interpretation that can scientifically resolve the DNA."
The Met Police said: "The investigation into the disappearance of Madeleine McCann remains ongoing. We are not providing a running commentary."
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