On January 17th, 2016, a volunteer died after taking part in a drugs trial in the west of France, while four others suffered suspected brain damage. The company who conducted the trial and supervisory authorities have insisted that the tragedy was “unprecedented” and could not have been foreseen. However, new evidence has emerged that a volunteer in a earlier trial with the same drug suffered side effects and that a later MRI scan shows he suffered a stroke. Yet this information appears to have been concealed by the medical and health authorities. Mediapart's science correspondent Michel de Pracontal reports.