Scotland’s top criminal court refused to overturn the murder conviction of the “Lockerbie bomber” in a 64-page appeal judgment released Friday.

A panel of five judges in the Scottish High Court of Justiciary upheld the late Abdelbaset Ali Mohmed al-Megrahi’s conviction for 270 counts of murder. The murders were committed in 1988 when Megrahi placed an explosive device onto Pan Am Flight 103, which subsequently exploded over Lockerbie in Scotland, killing 259 persons on board the airplane and 11 persons in Lockerbie from falling debris.

Following a reference from the Scottish Criminal Cases Review Commission, a body that addresses miscarriages of justice, Megrahi’s conviction was appealed on two grounds. Both grounds were rejected. The first ground was “whether the trial court’s verdict was unreasonable,” to which the court found that “a reasonable jury, properly directed, would have been entitled to return a guilty verdict.” The second ground was “whether the disclosure of certain material would have created a real possibility of a different (ie an acquittal) verdict,” to which the court said that “the contention that the Crown failed to disclose material which would have created a real prospect of a different verdict is rejected.”

“The bombing of Pan Am 103 is, to this day, the deadliest terrorist attack on UK soil and the largest homicide case Scotland’s prosecutors have ever encountered in terms of scale and of complexity,” Lord Advocate James Wolffe QC said in a media release. “The evidence gathered by Scottish, US and international law enforcement agencies has again been tested in the Appeal Court; and the conviction of Abdelbaset Ali Mohmed Al Megrahi stands.”

Megrahi insisted on his innocence throughout his life. Scottish authorities released him from imprisonment in 2009 on compassionate grounds following an advanced prostate cancer diagnosis. Megrahi lived a free man for almost three years after his compassionate release. The release was highly criticized, with one investigation undertaken by four US senators concluding that Megrahi’s three-month prognosis was “inaccurate and unsupported by medical science.” Megrahi served eight-and-a-half years of his life sentence before his compassionate release and death in 2012.

Although Megrahi is the only person currently convicted of the Lockerbie bombing, Wolffe re-iterated Scottish authorities’ commitment to identifying others involved in the Lockerbie bombing and commented that “there remain suspects under active investigation.”