Questions at the heart of Madeleine investigation

How significant is the McCanns' announcement that they are to have the hire car forensically tested themselves?

After a week under siege from Portuguese police, it is a major strike back from the couple which, according to Mark Williams-Thomas, a former police child protection officer, provides an insight into the mind games now being played by both sides in the case. "It's incredible that the police have not seized the car – and handed the McCanns this opportunity," he said.

Couldn't the police simply say that the McCanns had 'wiped' the car clean of evidence before the second tests start?

No, says Mr Williams-Thomas. "The McCanns' own analysts could demonstrate whether a cleaning up of evidence had taken place and could also determine whether or not a thorough examination of the car had been undertaken. The McCanns have definitely been given the upper hand by maintaining possession of the car."

What do we know about the forensic evidence found in the car?

The picture remains far from clear. Initial reports suggested a "99 per cent" DNA match, from blood found in the car but an officer took the unusual step of denying the report on which this was based. There has since been talk of an 80 per cent match from bodily fluids – but the statistics used have been odd. Forensic officers don't use percentages, but chances in a million, or billion, against a match.

Could Kate McCann's diary be important?

To those unfamiliar with criminal cases the idea of suspects revealing their crime by writing down their feelings about it in a diary might sound ridiculous. But many who commit serious crimes do write down incriminating details, in code or otherwise, according to Mr Williams-Thomas. "But the diary should also have been seized long ago," he said. "The disclosures in the media about how they want it would give Kate the chance to remove anything which might implicate herself.

How important is the planned search of a local church in Praia da Luz?

Many British observers believe this may simply be desperate talk from the Portuguese police, who insisted months ago that their search of the immediate area where Madeleine disappeared had come to nothing. Could the McCanns realistically have hidden a body right under the noses of police and media? Highly unlikely.