To simplify matters................
MARK Jobling is Professor in Genetics at the University of Leicester]
Sunday Mirror
The DNA clues.. vital questions are answered
Sep 9, 2007
by MARK JOBLING DNA expert
Q: Could the blood in the hire car belong to Madeleine?
A: Dead people don't bleed. So, if the blood was fresh when found by forensic experts, it clearly could not belong to Madeleine, who had been missing/dead for 25 days before the car was hired. We have to presume if Portuguese police think the blood is Madeleine's, then it was dry when found. The only way this could have got in to the boot of the hire car would have been if dried flecks fell off Madeleine's body. Under this scenario, her parents somehow killed Madeleine, stored her for 25 days and then used the car to dump her body secretly - despite being under the intense police and media spotlight. Alternatively, the parents could be being framed by someone planting Madeleine's blood.
Q: Why are the police asking the McCanns if it is Madeleine's blood?
A: A good question. In my opinion, if they had a complete DNA match with Madeleine's blood, they would simply charge Kate and Gerry. In 18 years' experience in this field, I have not heard of a case where police did not act immediately on evidence of that magnitude.
Q: Could the police be bluffing, then?
A: It would be a strange method for the police to use, but possible if they aren't sure it's Madeleine's blood. If the police do not have a full DNA profile, then it is feasible that they have a partial profile, which shares some of Madeleine's DNA strands.
This happens when the sample is too small to get a full profile or it is contaminated by somebody touching it or even a tiny drop of saliva falling on it. A method called Low Copy numbers is used for small samples. This will often give us a partial profile. If there are family members around, as in the McCanns' case, then things become even more complicated as all of the members of the family would share some aspects of their DNA. That could explain the police's tactics.
Q: Could scientists have made a mistake?
A: The Forensic Science Service in Birmingham which carried out the tests is a highly reputable and careful organisation. It is extremely unlikely that anything would have gone wrong once the sample reached them. Analysis of what is called short tandem repeats - which is the pattern of a person's DNA - allows us to build up a profile.
All people except identical twins have their own unique profile. If they get a full profile the chance of it being wrong is ridiculously small.
Q: How important is DNA?
A: DNA is a massively powerful tool in criminal cases, but it alone is not enough to convict a person. If it was Madeleine's blood in the back of that car then it places her at the scene. But it doesn't explain how she got there, who put her there or, if she died, how she did and who did it.
MARK Jobling is Professor in Genetics at the University of Leicester
http://themaddiecasefiles.com/post171133.html#p171133