The conviction of Abdelbaset Ali Mohmed al Megrahi for the bombing of Pan Am 103 over Lockerbie, killing 270 people, causes considerable unease among all who care about Scottish justice.

The authorised biography of Megrahi by John Ashton, a researcher for the defence team, brings together a number of claims that have already raised doubts about the handling of the case.

His allegation that Scottish Justice Secretary Kenny MacAskill personally urged Megrahi, through a private conversation with the Libyan foreign minister, to drop his appeal to assist his release on compassionate grounds, although denied, will re-ignite speculation that the Scottish Government was keen to prevent the appeal being heard. Megrahi was not required to drop the appeal for release on compassionate grounds. That he did so avoided considerable embarrassment for the Scottish justice system.

A number of allegations made by Mr Ashton potentially undermine the safety of the conviction. A key one is that a fragment of circuit board did not match boards linking the timer used to detonate the Lockerbie bomb with Megrahi. It is equally alarming, and already known, that Tony Gauci, the key witness for the Crown who testified Megrahi had bought clothes found near the bomb in his shop, had been offered a reward by the US Justice Department. Such tainted evidence would normally be inadmissible.

Also, the claim that Iran funded the Popular Front for the Liberation of Palestine General Command to carry out the bombing in retaliation for the American warship the USS Vincennes shooting down an Iranian passenger jet and killing all 300 people on board in 1988 is not new. But it, too, bears further scrutiny.

It is known that a number of documents were withheld from the defence, a practice no longer tenable following successful challenges in the Supreme Court. The most shocking evidential omission, however, concerned the break-in at Heathrow close to baggage to be loaded on to the flight the night before the bombing.

The Scottish Criminal Cases Review Commission (SCCRC) had already found six grounds on which Megrahi's conviction was potentially unsafe. Permission had been granted to publish the SCCRC's statement of grounds for appeal but this has not happened because the appeal was dropped. Whatever embarrassment would be caused by publication of the Commission's findings, the Scottish Government, which has already said it would publish, should recognise that this case has already called into question the quality of Scottish justice and that now is the time to release the document in the interests of justice.

For the families of those who died, the latest claims reinforce the cruel reality that, 23 years after that fateful night in December 1988, the investigation of the bombing remains unfinished business. Some of the relatives, most notably Dr Jim Swire, have shown extraordinary courage and tenacity in slowly gathering information about evidence not brought before the court. They deserve all the known facts to be brought together and examined in a public arena. Regardless of the difficulties in compelling witnesses to give evidence, an independent public inquiry remains the best hope of uncovering the truth.