Peter Kirkham, senior investigating officer on more than 20 murders, looks at four possible scenarios surrounding Maddy's disappearance.


THEORY ONE

Madeleine was killed, her body hidden before being moved in the boot of the McCanns' silver Renault Scenic

DCI Kirkham: This is what police will have been quizzing Kate about. You don't have some one in for 11 hours to check a few points. Portuguese police apparently believe Madeleine was killed by accident. That fits with the suggestion that her body could have been hidden for a while. If murder is pre-meditated, the killer has worked out what to do with the body. If it happens without planning, most people panic and either run, cover up how the death happened or hide the body. Small bodies can easily disappear down holes and even if you do not know the area you will not have to go far to find somewhere to dump it. Later, if you think you are getting away with it, there may be a temptation to return and dispose of the body before the search widens or somebody stumbles across it.

THEORY TWO

Kate and Gerry are being framed by the Portuguese police for the death, as several close relatives have claimed

DCI Kirkham: This is highly unlikely. Although Portuguese police made early mistakes, it is big leap to accuse them of fit ting up the McCanns. The crucial evidence is the DNA recovered by British police and tested in a British laboratory. If Madeleine's body had been found it would be possible for somebody to take her blood and plant traces to implicate somebody. But without a body where is the supply of blood cells from Madeleine?

THEORY THREE

The samples found in the Renault Scenic are from cross-contamination or accidental transfer, possibly from the McCanns' belongings

DCI Kirkham: This would be possible if the DNA samples were so small they could be identified as coming from a particular cell - blood, hair or sweat. A police officer could have picked up Madeleine's DNA on gloves during one search and not changed them immediately after placing the sample in the evidence bag. However there is a big "But" here. If the British scientists found blood cells and enough of them to know it was significant, it makes it very unlikely they are there by chance. Blood is very strong circumstantial evidence especially with a DNA match when it's found where it shouldn't be.

THEORY FOUR

Madeleine was abducted and her attacker used the same hire car which the McCanns later hired

DCI Kirkham: This is the million-to-one defence which someone who has all the evidence stacked against them would use. The Portuguese police should be checking who had that Scenic before, tracing them and inter viewing to make sure they had no explanation for having Madeleine's blood. If I was in charge of this investigation I would do it, but only to double and triple-check the case.