Which should take precedence: the wishes of foreign states or the tenets of Scottish criminal justice?

During the trial of the two Libyans at Zeist, the defence persuaded the court to request certain documents from the sovereign state of Syria.

These documents were held to be very significant to the defence of incrimination that had been lodged by the defendants' team.

That defence was centred on the widely held belief that it was not an MST 13 timer from a Zurich firm at all which had triggered the explosion, but a far simpler device originating from a terrorist facility on the outskirts of Damascus.

The actual explosion's timing corresponded perfectly with the devices which the defence had been unable to pursue.

Denied details of the alleged incrimination scenario by Syria, which replied to the court that the court had no right to ask it for any such information, the incrimination defence was badly damaged.

The prosecution case, in contrast, required the use of a sophisticated programmable timer capable of being set in Malta to survive many hours of flight and two changes of aircraft before exploding 38 minutes after leaving Heathrow. There are allegations now that the document at present held by the Crown, and refused to the defence, concerns such a timer. The MST 13 timer was capable of this performance, and the introduction of a fragment of one, found under somewhat mysterious circumstances and shown in court as exhibit PT35b, was the sole, and hotly disputed, evidence at Zeist for one having been used.

The court later heard details of the alternative timers, the use of which the defence had hoped Syria would corroborate. Extensive and thorough testing of these devices by German forensic scientists showed the Zeist court that these timers, made in the outskirts of Damascus, Syria, could not be adjusted by the user, and that if devices containing them were to be placed in an aircraft - no matter how long they might have waited at ground level - they were bound to initiate an explosion between 30 and 45 minutes after take off.

The fatal Lockerbie flight lasted 38 minutes.

In spite of Syrian hostility to the court's pursuit of further evidence, many observers felt the defence at Zeist failed adequately to pursue how such a device might have entered the belly of the 747 before it left Heathrow.

Thus, acceptance of the Crown case involved believing that the accused, acting in Malta, had set their MST 13 timer so that it exploded right in the middle of the fixed time window that was all that was possible for the Syrian-built units, if one of those, instead, had been introduced at Heathrow.

Yet the accused, if using an MST 13 timer from Malta, could just as easily have set it to explode over mid-Atlantic, rendering detailed forensic evidence unobtainable, and greatly reducing the risk of delays to flights.

The evidence-chain circumstances and forensic surroundings of the pivotal PT35b fragment from an MST 13 timer carry their own problems which no doubt the appeal will address and which it could be contemptuous to discuss here.

But now it is alleged that the mysterious document which the Crown holds but refuses to divulge to the defence, is withheld because "a sovereign state has forbidden its use".

One can sympathise with the Crown's dilemma: resolution of it requires a decision as to whether the wishes of a foreign power should override the interests of criminal justice in our own country. In that context we should remember that 11 citizens of Lockerbie were also murdered and their relatives also deserve to be confident that a fully competent process shall assess the case against their alleged murderers.

International justice needs to catch up with international terrorism. Not just in the international coordination of criminal investigations, which must be kept independent of nation-based intelligence services, but also in the powers accorded to the courts which must try the resulting cases.

In our burgeoning global village, would not a fitting tribute to the dead of Lockerbie, and assurance to the people of Scotland, be the redrafting of the status and powers of the International Criminal Court, of which the late Robin Cook was such a strong advocate?

There is still a long road to travel, with rocks and hard places on either side, before such a court can become the accepted arbiter of such dreadful cases.

Terrorism and global warming are now often compared as threats to our future. Both seem to demand an effectively empowered supra-national authority, just as the whole Lockerbie case demands an objective international inquiry.

Dr Jim Swire, Rowans Corner, Calf Lane, Chipping Campden, Gloucester.