The conviction of the Lockerbie bomber reaches a crunch point next week when a detailed review of the evidence is published that could force a second appeal or even a retrial.

The Scottish Criminal Cases Review Commission (SCCRC) is to announce on Thursday whether it believes the conviction was unsafe or whether a miscarriage of justice took place, following speculation that it has serious concerns about the use of evidence.

The case could put immense pressure on the Scottish justice system, for which the conviction of Abdelbaset Ali Mohmed al Megrahi was a massive test of global interest. It was tried in a special court without a jury at Camp Zeist in the Netherlands, which was designated Scottish territory for the purpose.

The Libyan intelligence officer was convicted in 2001 of the murder of 270 people after the bombing of PanAm flight 103 over Lockerbie on December 21, 1988. Eleven people were killed on the ground by falling wreckage and all 259 passengers and crew in the Boeing 747 died.

The SCCRC has the option either to refuse Megrahi's application or to refer it to the Court of Appeal in Edinburgh, where his conviction will be looked at again.

That would be the second appeal, after senior High Court judges dismissed a previous one in 2002 on a technical legal point. The report runs to 800 pages and will not be made public. A summary will, however, be published.

It was reported last Sunday that Megrahi's conviction will be declared unsafe and there will be a recommendation for the Appeal Court to reconsider the case.

Campaigners on Lockerbie have long had doubts about the case against Megrahi. Others have pointed the finger of blame instead at a Palestinian group backed by Iran.

The case of Megrahi, 55, sparked a political storm earlier this month between Tony Blair and Scotland's First Minister, Alex Salmond. Even before the SCCRC finding, Mr Salmond accused the Prime Minister of striking a deal with Libya that could see Megrahi transferred to a Libyan jail.

Tripoli's main motivation for the talks, it has been claimed, was to agree an exchange of specific prisoners: if Megrahi was allowed to serve the remainder of his life sentence in Libya then it would free five Bulgarian nurses and a Palestinian doctor sentenced to death for deliberately infecting children with HIV at Benghazi Hospital.

If Megrahi is cleared, the Libyans may claim back US$2.7bn (£1.4bn) in compensation paid to families of the Lockerbie victims - a bill that could fall to the Scottish Executive as being responsible for the justice system.

Dr Jim Swire, whose daughter Flora was killed in the bombing, said at the weekend: "I entered the court at Zeist at the beginning of the trial believing that this guy was responsible for killing my daughter. Having listened to the evidence, I came away convinced that Megrahi was a scapegoat and should never have been convicted."