A prosecutor on Monday accused three Britons of scouting out potential targets on behalf of suicide bombers who killed 52 commuters in the 2005 London bombings. The three defendants pleaded not guilty. Waheed Ali, 25, Sadeer Saleem, 28, and Mohammed Shakil, 32 are being retried on a charge of conspiring to cause explosions with the bombers who blew themselves up aboard three subway trains and a bus on July 7, 2005. Prosecution lawyer Neil Flewitt said that the three defendants had “conducted hostile reconnaissance of potential targets” during a visit to London seven months before the transit attacks.