Justice should be tempered by mercy. That was the thinking of the government of Scotland when it decided to release Abdel Basset al-Megrahi, who is suffering from terminal cancer, from prison, eight years into a 27-year minimum sentence for blowing up an airliner over Lockerbie, Scotland, and killing 270 people.

But that show of humanity has unleashed a firestorm of controversy. Critics argue that compassion from the government should be matched by a similar demonstration by al-Megrahi himself, a step he has never taken. More disturbing still are reports that the Scottish decision was influenced by the British government's desire to improve ties with Libya. London has vehemently denied the accusation, but questions linger, clouding an already emotional and difficult decision.

Pan Am flight 103 exploded in midair over Lockerbie, Scotland, in December 1988, claiming 270 lives. The atrocity triggered the largest law enforcement investigation in British history, one that concluded in murder indictments against al-Megrahi, then a Libyan intelligence officer, and Mr. Lamin Khalifah Fhiman, the Libyan Arab Airlines station manager in Malta. After protracted negotiations with the Libyan government, the two men were handed over and a special court was convened in 1999. In January 2001, the court found al-Megrahi guilty of murder while acquitting Mr. Fhimah. Eight years into his sentence, al-Megrahi was released on compassionate grounds: He suffers from prostate cancer and is said to have but three months to live.