Salacious reports of blood spots, intercepted phone calls and child sedation so far have been dismissed as nothing more than libellous slurs by the McCann family.

Now there is the very real prospect that Kate McCann be charged and tried over Madeleine's disappearance.

But any suggestion that Mrs McCann accidentally killed her daughter by some unknown means, then hid her body for almost a month before disposing of it using a hire car, is not only vigorously denied by the family but raises more questions than answers.

Traces of dried blood, said to be Madeleine's, have allegedly been found in a car hired by the McCanns 25 days after Madeleine's disappearance.

The blood is said to have been found in the boot of the Renault Scenic hire car after sniffer dogs were brought in by British police as part of a review of the investigation.

Tests by the Forensic Science Service in Birmingham are thought to have indicated the blood may be Madeleine's.

Unsubstantiated reports in one Portuguese newspaper claimed the dogs also detected 'the strong scent of a corpse' on the keys to the car. The same dogs found blood spots in the McCanns' apartment, which were later found not to be Madeleine's.

There were also reports that the dogs had picked up a trail on a beach near Praia da Luz, leading to speculation that a body had been dumped at sea.

Then last month there were speculative claims that the McCanns, both doctors, may have 'doped' Madeleine to get her off to sleep before they set off for dinner at a tapas bar near the apartment.

There were reports today that the police were questioning Mrs McCann about giving Madeleine a dose of a sedative.

Portuguese newspapers also claimed that police had 'intercepted' phone calls and emails between the McCanns and their friends.

Throughout the investigation police found no forensic evidence of an intruder in the McCanns' apartment, and there were no consistent witness accounts of a suspect being seen near the apartment at the relevant time, reinforcing the theory that no-one else was involved.

The case for the defence

Mrs McCann's lawyers will already have identified several huge holes in the theory that she could have killed Madeleine.

How, for example, could she have killed her daughter, removed her body from the apartment and hidden it while her friends sat just yards away in a tapas bar?

And how, four weeks later, was one of the most watched women in the world able to bundle a body into a hire car and dispose of it under the noses of her family, police liaison officers and the world's press?

Nor have the police offered any suggestions so far as to how Madeleine may have died - something they will be unable to do unless her body is found.

The McCanns were among a party of nine people on the day Madeleine disappeared, in a resort full of tourists, and were never away from their friends for more than a few minutes at a time.

It would surely have been impossible for Mrs McCann to kill her daughter and hide the body in such a short space of time without being seen, not to mention returning to the restaurant as if nothing had happened.

The only other window of opportunity would have been in the two and half hours between the time when Madeleine was last seen alive and when the couple met their friends for dinner.

Again, is it really possible that Mrs McCann could have killed her daughter, hidden her body and shown no signs of anxiety? Where was her husband Gerry at the time?

Most implausible of all, perhaps, is the suggestion that Mrs McCann returned to the place where she had hidden the body a month later, put it in the boot of her hire car and driven somewhere to dispose of the body.

Ever since Madeleine's disappearance the McCanns have been surrounded by friends and family, police officers and the media - are we to believe that she somehow gave them all the slip and buried her daughter or threw her out to sea?

Furthermore, could she really have gone through 127 days of constant interviews and media exposure without once showing any signs of guilt?

On a procedural level, a catalogue of blunders by the police, who failed to seal off the crime scene, would be likely to render any forensic evidence unreliable.