Gerry and Kate McCann can count themselves lucky it was in Praia da Luz and not in Portrush that their daughter disappeared. Had it happened here, they might now be on remand, awaiting trial. Which is not to say that either of them is guilty of anything, but that the evidence which we are told Portuguese police have available would have been enough to bring charges in this jurisdiction.
Evidence of the same sort has been the basis of charges against unemployed south Armagh electrician Sean Hoey. He's in prison awaiting a verdict following trial for 58 alleged offences, including 29 of murder in Omagh on August 15, 1998.
The key evidence against Hoey consists of low copy number DNA (LCN/DNA), allegedly linking him to bombs. It's the category of evidence which reports have suggested proves that Madeleine McCann's body was at some point in the boot of a car hired by her parents 25 days after her disappearance. LCN/DNA refers to a technique whereby a DNA profile can be extracted from a body sample of a few cells thousands of times smaller than a grain of salt. Uncertainty as to the strength of LCN/DNA evidence emerged at Belfast Crown Court during Hoey's trial last December when Mr Justice Weir told prosecution witness Dr Peter Gill, a leading advocate of the use of LCN/DNA, that parts of his evidence were "very unhelpful" . Dr Gill had conceded that some of the results presented at the trial as pointing to Hoey's guilt were, in themselves, "valueless".
Pressed by Mr Justice Weir to say clearly what weight should be given to which parts of the LCN/DNA evidence, Dr Gill responded that this was a complex area in which there were "shades of grey".
Professor Allan Jamieson, for the defence, dismissed LCN/DNA as "unreliable" and test results from it as "open to interpretation".
Uncertainty about the value of LCN/DNA goes some way towards explaining apparent contradictions in reports from Praia da Luz in recent weeks. An announcement on Sky News that DNA samples found in the hired car "fully matched" the missing four-year-old was taken by many as establishing that her parents, at the least, had been involved in her disappearance.
When Portugal's national police chief Alipio Ribeiro on the following day described the results of the same tests as "not conclusive", it sounded to some like a cop-out, a reluctance to face facts devastating to the McCanns. But not necessarily so. The fact he may have been facing was the absence of scientific consensus on the dependability of LCN/DNA. The result of the tests may have been that the reported car-boot sample " fully matched" the missing child. But the scientific basis of the tests themselves was by no means universally accepted.
The lack of consensus underlies disparities in the way LCN/DNA evidence is handled in different jurisdictions.
In the House of Commons in February this year, Lib-Dem Hornsey MP Lynne Featherstone asked what the criteria was for mounting criminal cases on the basis of LCN/DNA. Home Office Minister Joan Ryan replied: "The Crown Prosecution Service make it very clear that in every case involving a DNA profile, there must also be appropriate supporting evidence before a case can succeed. It follows that any prosecution should be based on a DNA profile and other admissible and credible evidence."
The McCanns, in other words, if DNA evidence was all there was against them, wouldn't be charged in Britain. And neither, possibly, would Sean Hoey have been.
The Northern Ireland anomaly was the subject of an exchange of letters last April between the Public Prosecution Service (PPS) and solicitors acting for another man charged with a serious offence. In an explanation which many might consider remarkable, the PPS wrote that, "There is no stated policy in the PPS in respect of DNA evidence with regard to prosecutions. The Crown Prosecution Service policy is not binding on the PPS".
This raises the question of who, given that the administration of justice is not a devolved matter, decided on the adoption here of a policy (or 'no policy') on a not insignificant matter at variance with existing policy across the water. If it turns out that charges are laid against the McCanns while they are in England - perhaps by the posse of Portuguese police reported, even as I write, to be making hot-foot for the quiet town of Rothley - they might have a sound case for resisting extradition on the grounds that the evidence offered against them would not provide a basis for similar charges to be brought under English law as it is currently administered.
If this scenario, or something akin, were to unfold, the Leicestershire doctors wouldn't be wanting for support. On Newsnight eight days ago, the man widely credited with inventing the DNA test, Sir Alec Jeffreys, said that, on the basis of the reported evidence, he would be willing, if asked, to testify for the McCanns.
We are told we are all equal before the law, irrespective of background and however atrocious the crime we are charged with.
The social standing of the McCanns, or the part of the UK they happen to be resident in, shouldn't entitle them to more favourable consideration than is accorded to, for example, an unemployed electrician from Jonesborough.