Don't you wonder what that "source" was?
There's no record of a sample ever being taken from Murat's car because the "sniffer dogs" alerted to the Renault Scenic.
The dogs had been brought back to Portugal and when they alerted, (I don't know what precipitated bringing them back) the police searched the trunk of the car more thoroughly and found the sample under the mat/wheel well kind of area--not really clear what, but not the top surface of the trunk.
The tests were done at two independent labs in Great Britain.
With such a high-profile case, every precaution would be taken to process the tests according to established procedure.
As yourself what "source" would have suggested that a mix up would be possible--knowing full well there were not multiple samples of Madeleine's DNA sitting around in unlabeled containers with a stack of labels near by, like file folders full of papers or something.
This is a page right out of the O.J. Simpson defense and obviously, it worked really well for him. All you need is a little confusion about collecting and testing forensic evidence, repeating something loudly and often even if it's incorrect, and an audience willing to believe.
As always, Texana, you have earned my respect. I appreciate your thought processes. :clap: