Megrahi has launched a second appeal against his conviction
The legal team for the man convicted of the Lockerbie bombing has told judges that the evidence against him was "wholly circumstantial".
Abdelbasset Ali al-Megrahi, 57, who has prostate cancer, was not in court as his second appeal got under way.
However his QC, Maggie Scott, said he could follow proceedings via live video link to Greenock Prison.
She told the Court of Appeal that it remained Megrahi's view that he had suffered a "miscarriage of justice".
The second appeal is being heard by five judges in Edinburgh, headed by Scotland's senior judge, the Lord Justice General, Lord Hamilton.
Miss Scott said that because of his cancer Megrahi would need to take breaks due to the pain and was set to see doctors later this week for a new course of treatment.
She told the court: "The appellant's position is that there has been a miscarriage of justice.
"The trial court, on the basis of wholly circumstantial evidence, concluded beyond reasonable doubt that the appellant was involved in the commission of this crime.
"Our submission is it was wrong to do so".
She argued that the guilty verdict against Megrahi depended upon four "critical inferences" drawn at his trial at Camp Zeist in the Netherlands.
Miss Scott said these included that Megrahi was the buyer of clothing remnants of which were found in the suitcase containing the bomb and that the purchase was made on 7 December, 1988.
She said it was also inferred that the purchaser knew the purpose for which the clothing was bought and that the suitcase containing the improvised explosive device was "ingested" at Luqa airport in Malta.
The defence counsel argued that they were not sufficiently supported by accepted evidence and relied on defective reasoning.
January 2001: Megrahi convicted
March 2002: Appeal rejected
June 2007 "Conviction unsafe"
October 2008: Cancer diagnosed
She said: "In this wholly circumstantial case the critical inferences are not the only reasonable inferences that could have been drawn from the accepted evidence."
She said they were insufficient in law to support the guilty verdict returned against Megrahi.
The first part of his hearing is expected to last four weeks with further stages in the process taking it into next year.
He has already lost one appeal against his conviction for the 1988 atrocity in which 270 people died.
Since then he has been in prison in Scotland, and must remain in jail until at least 2026.
In 2007, after a four-year investigation, a second appeal was ordered by the Scottish Criminal Cases Review Commission, which said Megrahi's conviction "may be unsafe".
He is currently held in Greenock Prison, where he was diagnosed as suffering from terminal prostate cancer.
In October 2008, appeal court judges rejected his plea to be released from jail on compassionate grounds.