Both the Birmingham Forensic Science Service and the Portugese police are officially refusing to comment on what samples have been found and how important they could be. But at the same time, information has been systematically leaked to the press, leading to an unprecedented level of forensic speculation worldwide.

What does the 'substantial' amount of Madeleine's hair said to have been found in the boot of the car signify? How could blood or other bodily fluid have come to be in a car hired 25 days after Madeleine's disappearance? Does it matter that scientists in Birmingham are relying on Low Copy Number (LCN) DNA rather than 'normal' DNA?

According to Alan Baker of Bericon Forensic Sciences in the UK, a scientist is only as good as the samples found and the fact that Madeleine's hair is said to have been found in the car is not particularly significant.

"They say they found a substantial amount of hair in the car, but we don't know whether that is 10 strands, or 20 or 50, " he told the Sunday Tribune. "If it was a clump of Madeleine's hair then that would raise other issues, but, otherwise, hair can transfer from clothes or other members of the family. And without the hair follicle, it's not possible to get any DNA from it."

There were reports early last week that blood had been found in the McCann's hired car, with police saying it was a "100% match" to Madeleine's.

But later in the week, reports emerged that it was 'bodily fluid'. There is a theory, however, that because the McCanns moved Madeleine's belongings in that car when they were changing apartments, her DNA could have transferred via her belongings.

"From a forensic point of view, if blood was found in the car that would be potentially very significant, " said Baker. "If it was saliva or sweat then that is harder to analyse. Dried blood could have been transferred from clothing put into the car, but the chances of saliva transferring are unlikely.

It all comes down to the quality of the DNA they have got."

Dr Louise McKenna, deputy director of the Irish Forensic Science Laboratory, who spoke in general terms on DNA samples, agreed that hair is not particularly good evidence as children share the same hair DNA as their mother. She also emphasised that when the Irish lab gives evidence on a DNA match, they would always preclude family members.

"For instance, we would describe the closest kind of match by saying this DNA profile is seen in less than 1000 million of the population unless it's from a close relative of the victim, " she said. "But it has to be evaluated very much in the context of the situation. So if DNA is found on something that the victim or perpetrator was unlikely to come into contact with then that can be more significant."

In Madeleine's case, scientists at the Birmingham lab are said to have analysed LCN DNA, a method that was developed in that lab by John Whitaker and which has been cited as unreliable in every country in the world except the UK and New Zealand.

Normally, DNA is amplified 28 times for analysis, while LCN DNA is amplified 34 times. According to Dr Katrin Both at the Forensic Science Service in Adelaide, Australia, LCN DNA is unreliable and can pick up spurious DNA that is irrelevant to the case.

"There is a big move away from LCN DNA taking place around the world and I think it is on its way out, " she told the Sunday Tribune. "I was at a conference chaired by John Whitaker in Copenhagan recently and he seemed to be backing away from LCN DNA and talking much more about low levels of DNA rather than low copy numbers. It is a very sensitive method that can often throw up unreliable results."

LCN DNA was brought up in the trial of Wayne O'Donoghue for the murder of Robert Holohan and subsequently dismissed by the trial judge as unreliable.

"We do not deal with LCN DNA over here, " said McKenna. "Because the DNA is so much more amplified, it shows up stray DNA that can be much more difficult to interpret."

The intensity of speculation around the Madeleine McCann case is such that every average punter is now waxing lyrical about DNA and what it means in this case.

"Much as I love interest in my science, the McCann case has definitely got out of hand, " said Baker. "If this crime had happened in the UK, no one would have been able to hear the evidence until the court case and that's the way it should be.

"As it is, we have conflicting information being leaked to the media that is incredibly unhelpful and unfair to everyone involved in the case, especially the McCanns."