Of Moroccan nationality, Belhadj is accused of being one of the intellectual authors of the train bombings, along with Rabei Osman El Sayed Ahmed and Hassan El Haski. With charges of belonging to a terrorist group, the murder of 191 persons, and the attempted murder of 1824 - the total sentence requested by the prosecution is 38656 years.
Belhadj is believed by the Spanish police to be the spokesperson of Al-Qaeda in Europe, and the person who is believed to have made the claim for responsibility for the bombings in a video recovered from a waste paper bin near to the M-30 ring road in Madrid. His nephews Mohamed and Brahim Moussaten are also on trial facing lesser charges of collaboration with a terrorist organisation.
He was arrested on the 19th March 2004 in Belgium as part of a police operation against the Moroccan Islamic Combat Group, and was extradited to Spain in April of 2005. The judicial investigation accuses him of being in possession of telephone numbers of members of the group responsible for the bombings, and claims that he was in Spain in February 2004, the month before the train attacks.