A lack of inhibition must come easily when your parent is one of the world's more resilient dictators. Why fib when people rarely contest a word you say? If your dad is Colonel Muammar Gaddafi, Libya's unchallenged leader and new best friend to the West, you can tell the truth - or not - without much fear of the consequences.

Comments last week to French newspaper Le Monde by Saif al Islam, Gaddafi's 35-year-old son, amounted to an interesting parable, I think, for the democracies of the West. Faced with terrorism and an abundance of threats, they have become economical, to put it kindly, in their use of truth. Just possibly, just once or twice, they have not told us quite everything about reasons and risks. Young Saif, in contrast, enjoys the luxury of frankness.

So, was a deal struck between Tony Blair and Gaddafi to engineer the repatriation of Abdelbaset Ali Mohmed al-Megrahi, the "Lockerbie bomber"? That question caused some trouble earlier in the year, you'll recall, when Alex Salmond complained about failures of communication between London and Edinburgh on the issue.

London said, and continues to say, that any decision concerning the prisoner was, and is, "a matter for the Scottish courts and Scottish authorities". Edinburgh said that it would defend the integrity of a legal system already debauched, as it happened, by Megrahi's farcical trial in the Hague. Last week, Saif said in Nice (more or less, for my Arabic isn't up to much): "A deal? Of course."

Saif proclaimed himself confident that Megrahi will soon be returned to Libya and took satisfaction from a developing extradition arrangement between his country and Britain. How does that square, precisely, with all the Downing Street denials, the rubbishing of Salmond's "grandstanding", and the continuing insistence that Scots law remains paramount?

Surely it could not be possible or likely that someone - let's say a departing prime minister - failed to tell us the whole truth? Where Lockerbie is concerned, the difference between likely and probable is paper-thin.

There are complications, of course. The first is fundamental: Megrahi didn't do it. There is not the space here to explain why the man in Greenock Prison did not procure the murders of 270 people on Pan Am flight 103in December 1988. For now, I merely assert that the evidence presented in the Hague would have been laughable in any other circumstance. Scots law disgraced itself in those compromised proceedings.

That being so, however, the Court of Appeal will soon have to decide whether to accept a recommendation from the Scottish Criminal Cases Review Commission calling for the evidence in the Lockerbie trial to be re-examined. The definition of "flimsy" is about to be tested. All the lawyers of my acquaintance say that, in due course, Megrahi will surely walk free, if he is not shipped out of Scotland beforehand.

So what then? Are we asked to believe that the worst atrocity ever inflicted on Scotland involved not a single perpetrator? That a long, allegedly intense, international investigation resulted in nothing better than the persecution of one innocent man? And that a Scottish court, in all its majesty, returned a guilty verdict on such a basis?

To put it no higher: a quick extradition deal, and a few more lies to conceal Blair's untruths, won't cover this. It amounts to an unholy shambles, the unravelling of almost two decades of deceit. Just imagine what follows if "the evidence" is truly re-examined with proper care.

Megrahi was convicted, supposedly after the most thorough investigation the police and security forces of the West could muster. Now the Libyans - those trusting souls - reckon that Blair gave his word guaranteeing the return of the only person we ever managed to convict. Scotland's legal system, and hence the Scottish Executive, therefore have some astonishing questions to answer.

Jack Straw, Westminster's new justice secretary, may have brought a little clarity to relationships between Edinburgh and London since Blair's departure, so it is said, but that hardly alters fundamentals. Sometimes the law misfires: we know this. Sometimes, though, the entire system we seek to defend against terrorists (or politicians) gets bent out of recognition. Corrupted in its own defence: that's almost an epitaph.

The wrong guy was the only guy. Worse, all those who failed to name the actual culprits, thanks to incompetence or intent, face no interrogation. Increasingly, Lockerbie resembles a political-management precursor to our manipulated post-11 September, 2001 world: pick your villain, pick your story, then bend your laws, your politics, and your media to fit. Democracy.

I tried this question in various formulations: are people secure if they cease to believe those defending their security? Can you be defended, truly, by those who lie about your defences, and the need for defence? If we are denied truth, what remains but lies? Who did bomb Lockerbie, and why have a succession of career bastards spent almost 20 years evading the question?

The tree-protected memorial that stands near the little town, amid those wind-blown, moss-green hills, will take your breath away. A "why" this happened is easy - causes are ten a penny. The "how" is harder. How did someone do the thing, how did others agree to it, and how do others still go on cultivating the lies, under democratic sanction, two decades on?

The family and friends of Jean Charles de Menezes may wonder about that. Had you listened late last week to Sir Ian Blair, the lead man at the Metropolitan Police, you would have heard "Britain's top cop" insisting that he had no knowledge whatever of the assassination of a 27-year-old Brazilian in 2005. Not a clue. Not one of his subordinates passed the word of the hit. Believable?

You would also have heard Blair denying that he was telling the public about vast terrorist threats with no understanding of - in the language of the Independent Police Complaints Commission - a "ghastly mistake" at Stockwell Tube station. Assistant commissioner, Andy Heyman, meanwhile, misled no-one; or misled them with the best of intentions; or misled them while enjoying the full support of a superior who, of course, knew nothing about anything. And so forth.

The people in these islands will cope with a very great deal if someone would, just once, honour them with the truth. We know that things go wrong. We know that mistakes are made. We strain to believe that those who defend us would allow a Pan Am jet to be dropped on a small Scottish town.

We wonder, though. Menezes died thanks, we hope to believe, to procedures in need of revision. At a long stretch, most of us would probably accept that he died because of a horrible error committed for the best of reasons. So why the deluge of excuses? Had an authentic terrorist chosen the best possible way to undermine the British public's will to resist, the jihadi would have selected last week's dire remarks by Sir Ian Blair.

Truth is fundamental. Truth is, they tell us, our distinguishing feature as a democracy. It was once the shining virtue of Scotland's jurisprudence. That was the least of Lockerbie's collateral damage, but not the least significant.

Are not the people of this little country entitled to the moral right to know, finally, who bombed Pan Am 103?

If there is no answer, I know, finally, what I think: they lied; they lie.