A restaurateur had a terrorist handbook on how to be a "secret agent" living a double life in the West, a court heard.
Abdul Hussain, from Torquay, Devon, is accused of having a stash of IS propaganda and terror documents.
The 41-year-old, claimed he had an "ingrained curiosity" about the Islamic State group (IS), the war in Syria and extremism.
Mr Hussain denies two counts of possessing information likely to be useful for terrorist purposes.
The Old Bailey heard the defendant claimed he was researching the subject for a documentary but prosecutors have argued this was not a reasonable excuse.
Prosecutor Paul Raudnitz said: "The prosecution raise an eyebrow over whether the claim he was laying the groundwork for a documentary was in any event true.
"That may be the issue for you to decide in this case."
The court heard Mr Hussain's home was raided in July 2018 and police seized his computer hard drives.
They were found to contain a large number of documents downloaded from the internet, including a "very large number" said to relate to conflicts in Syria and Iraq, IS and terrorism.
Videos portraying "disturbing scenes" of IS fighters training and "extremely savage" executions, were also uncovered, the court heard.
Documents entitled How to Survive in the West - A Mujahid Guide (2015) and Miracles in Syria crossed the line into breaking the law because they contained information useful to a terrorist, prosecutors said.
Jurors heard the July 2018 raid came after the discovery of IS propaganda during a search of Mr Hussain's restaurant in Exeter in November 2017.
The trial continues.