The former Libyan intelligence officer Megrahi was the only person convicted for the bombing Pan Am Flight 103
Five senior judges on Thursday began deliberating their ruling in a posthumous appeal against the conviction of Lockerbie bomber Abdelbaset Mohmet Al-Megrahi.
Scotland's most senior judge, Lord Justice General Colin Sutherland, said the panel would issue a written opinion "as soon as it possibly can" after three days of submissions.
The former Libyan intelligence officer Megrahi was the only person convicted for the bombing Pan Am Flight 103, which blew up over the Scottish town of Lockerbie on December 21, 1988.
A total of 270 people were killed, including 11 on the ground, in what remains Britain's worst terrorist attack.
Megrahi was jailed for life in 2001 but maintained his innocence until his death in 2012. His family has taken on the case and in March won the right to take it back to court.
An independent criminal cases review body said a miscarriage of justice may have occurred on the grounds of "unreasonable verdict" and the withholding of evidence from the defence.
But on Thursday, the five judges on the High Court of Justiciary in Edinburgh were told in a remote hearing that the three judges who tried and convicted Megrahi were entitled to infer he was involved.
Lawyer Ronald Clancy said Megrahi's use of a false passport was part of a "significant chapter of evidence" supporting his involvement in the atrocity.
Megrahi used the document to travel to Malta, from where a plane carrying the bomb departed before the attack, and which was "connected to the planting of the device."
"We say that was an entirely legitimate inference to draw, certainly well within the range of inferences open to a reasonable jury," he told the court.
Claire Mitchell, representing the family, had argued the process used to identify Megrahi was "highly prejudicial" and should not have been given the weight that it was.
A key witness had seen a photograph of Megrahi in a magazine article suggesting his involvement shortly before the trial, she said on Wednesday.
She also said prosecutors in the trial, which was held under Scots law at a special court in the Netherlands, had not proved Megrahi bought the clothing found in the bomb suitcase.
There was doubt, too, about the dates of his visit to Malta and as such "no reasonable jury" could have returned a guilty verdict, she added.
Clancy countered claims that the identification witness -- Maltese shop owner Tony Gauci -- was motivated by a possible reward as he was "not compensated."
The High Court has upheld a secrecy order signed in August by UK Foreign Secretary Dominic Raab to withhold intelligence documents related to the case on national security grounds.
His predecessor in 2008, David Miliband, did the same before Megrahi's second appeal, that was later abandoned after his diagnosis with terminal cancer.
The Megrahi family, whose case is supported by some of the victims' families, believe the documents are central to proving he was not involved.
It has been claimed Iran used a Syria-based Palestinian proxy to build the bomb that downed the Boeing 747 as it travelled from London to New York.
Iran is said to have wanted revenge for a US Navy strike on an Iranian Airbus six months earlier in which 290 people died.