Key witness EVAN Kohlmann, an FBI consultant flown from the US as an expert witness, played a pivotal part in explaining the significance of the inflammatory material at the centre of the case.

While the Crown conceded that video clips and documents discovered on Mohammed Atif Siddique's computer were widely available and could have been obtained by anyone using an internet search engine, Mr Kohlmann argued that they were typical of the material exchanged by serious terrorists.

For nearly four years, Mr Kohlmann has run, described as an "information clearing house" which allows academics and investigators access to statements and videos issued by al Qaeda and affiliated groups.

A politics and law graduate from Georgetown University, Mr Kohlmann has lectured to law enforcement agencies in America, Australia and Britain. His testimony has helped convict a string of terrorists in the US and he has previously appeared as an expert witness in an English terrorism trial.

He has played a leading role in the counter-terrorism organisation Nine/Eleven Finding Answers, which seeks to expand knowledge of Islamic extremist groups. His book, Al Qaeda's Jihad in Europe: The Afghan-Bosnian Network, details how militants from Afghanistan used the Bosnian war to expand into North America and Europe.

Mr Kohlmann told jurors that Siddique's propaganda videos and documents containing wordy ideological arguments supporting suicide bombings were usually exchanged on locked-down websites used by al Qaeda's online division. One video, by the Iraqi Martyrdom Battalion, was translated into English in January 2006 and found on Siddique's laptop two months later when police detained him at Glasgow Airport.

Another, found on a CD under the carpet in Siddique's home, was called Qahr Us Saleeb - translated as Crushing the Cross. It featured the voice of Osama bin Laden and an Australian radical denouncing the West.

Mr Kohlmann said it was accessible via a website open for only a matter of days, notification of which was advised through Islamic password-protected forums. A counter-terrorism website run by a former Israeli intelligence officer,, was also found to have links to radical Islamic online magazines.