The regrets of a cancer expert who assessed the only man ever convicted of the 1988 Lockerbie jetliner bombing have intensified the anger felt by victims' relatives over Scotland's decision to release the Libyan on compassionate grounds.

Professor Karol Sikora and other experts had said Abdel Baset al-Megrahi probably had only three months to live when he was freed from a Scottish jail last August and allowed to return home to Libya. But one year later, Al-Megrahi, who is being treated for prostate cancer, is still alive.

Sikora, one of three experts who assessed al-Megrahi's health for Libyan authorities, was quoted by Britain's Observer newspaper Sunday as saying he should have been more cautious about the chances of survival.

"If I could go back in time, I would have probably been more vague and tried to emphasize the statistical chances and not hard fact," Sikora was quoted as saying.

Scottish authorities deny that the opinions of Sikora and the other experts who advised Libya entered into the decision to release al-Megrahi, though families contend that the advice must have played a role.

"It's obvious the whole thing was flawed," said Frank Duggan, president of the Victims of Pan Am Flight 103, an advocacy group that represents some of the families of those killed.

Duggan said Scottish Justice Secretary Kenny MacAskill had rejected a U.S. government request to commission an independent medical examination of al-Megrahi, and also has declined demands from families to publish in full the advice Scotland received from consultants.

Al-Megrahi is the only person to have been jailed for the 1988 bombing of Pan Am Flight 103 above the small Scottish town of Lockerbie, which killed 259 people -- mostly Americans -- onboard and 11 on the ground.

He was convicted in 2001 and sentenced to serve at least 27 years in a Scottish prison, but released in August 2009 on compassionate grounds.