Five months after her disappearance, we are no further towards knowing exactly what happened to Madeleine McCann and we may never know the truth. However, after spending many days in Praia da Luz while making a Dispatches documentary about the case, I have come to the conclusion that the greatest likelihood is that she was abducted, and probably by a local person.

There are a number of indicators that have led me to this conclusion.

The days that I spent in Praia da Luz speaking to those who were there soon after that dreadful night in May, and with experienced police officers and a forensic scientist, have helped to clear away many of the myths and half-truths that have driven the accounts of Madeleine’s disappearance.

If you stand outside the apparently unremarkable apartment from which Madeleine vanished, the reality of unexpected horror hits home. The tidy walls and hedges that divide the apartments from the swimming pool, on the far side of which the family were eating tapas on May 3, take on a much more sinister form when you realise that they hide any clear view of the room in which the McCann children were sleeping.

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An abductor who knew the complex would have had to be quick to remove the child from her apartment without being seen, but he could have done it. After passing through the alleyway that ran beside the apartment, he would then have found it simple to dash across the deserted road behind the resort and through a small car park to a network of alleyways sheltered by high walls.

These alleyways, decorated with lush bougainvillea, provide an ideal rat-run that would be well known to local criminals. Late in the evening it would have been a simple thing to pass through these alleyways to a safe house or a car parked near by.

Possible escape routes aside, one of the most convincing arguments I have heard for an abduction by a local came from my colleague at Liverpool University, Professor Kevin Browne, who advises many international agencies including the WHO and Unicef on child protection. He made clear that this quiet village could harbour a number of child abusers who had been released into the community rather than convicted.

The situation in Portugal was, he pointed out, very different from that in Britain today, being more the way it used to be here a decade or more ago.

Compared with other countries in Western Europe, Portugal convicts a much smaller proportion of child abusers. Children are more likely to be removed from their families, ending up in institutions while their abusers walk free. As a consequence, there are not only potentially more abusers within society unmarked and unmonitored, but a of whole new generation of people with an increased likelihood of becoming abusers because of their own experiences.

There are limited possibilities for what happened to Madeleine. I think of these along a continuum from those, at one end, in which she played a significant role, to the other extreme at which would lie an organised network of traffickers who come to Praia de Luz specifically to find a victim.

The family or close associates distance us from the possibilites involving the girl herself. Those who know the family but are not really known to the family themselves, such as service staff, lead us a step closer to the possibilities of a distant criminal network.

However, there is a crucial prospect of a person who had no direct contact with the family, observing them from afar, although not part of any criminal organisation.

Each possible explanation for the disappearance is driven by different assumptions.

If she had woken up in distress would she have sat and cried or wandered off into the town? If she had wandered off it would have been to try to find her parents – along a probably familiar route to where they were eating. It would have been a terrible coincidence if she had been abducted on such an unlikely journey.

The prospect of family or friends’ involvement beggars belief. For a start, if the child had been killed in some accident, possibly as a result of an overdose, then her medically trained parents would have had to be exceptionally incompetent, for which there is no evidence. Furthermore, the friends who were with them would all have had to be willing to risk their professional careers to keep such a appalling secret for such a long time.

Organised networks of people traffickers, sadly, have much more obvious opportunities for finding vulnerable children who would not be missed on the streets of many developing countries, or even in the orphanages, and sometimes the streets of Eastern Europe. Why risk being caught in a quite middle-class holiday resort?

Against this backdrop, it became clear to me that the police in the Al-garve simply do not have the resources to deal with crimes of this magnitude. Their expertise lies in dealing with the drug smuggling that occurs frequently between North Africa and here. But resources that the English police can bring to bear quickly are unlikely to be available to the Portuguese police in any serious inquiry.

Detective Chief Superintendent Chris Stevenson, who headed the Soham investigation into the murders of Holly Wells and Jessica Chapman in 2002, made clear in his contribution to the documentary that the British police would have followed the detailed procedure laid down in an inch-thick “murder manual” – a painstakingly systematic approach that can send the cost of the average murder inquiry to £1 million.

Without these resources, the Portuguese police have had to proceed very differently. They have to find ways of taking the short cuts that detectives in fact and fiction have always had to take in the past. This consists of forming a view of what the likely cause of the crime is and using that in the search for clues.

For me the most obvious possibility is the local offender quickly escaping down the rat-run of dark alleys. One witness is reported as seeing a man rushing away from the complex with a child wrapped in a blanket shortly after the last reported sighting of Madeleine.

The days spent discussing the disappearance of Madeleine in the actual location where the McCanns had been on holiday provided a rather different perspective from the one heralded in the British media. The little girl may just have been in the wrong place at the wrong time.

Searching for Madeleine: A Dispatches special on Channel 4 tonight at 9pm

David Canter is a criminal psychologist

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