Justin Bieber -- 'Harassed and Stalked' By Dead Photog

Justin Bieber was stalked and harassed by the photographer who was killed while taking pictures of the singer's car on New Year's Day, and he lied about J.B. smoking pot ... sources connected with Bieber tell TMZ.

Our well-connected Bieber sources tell TMZ ... photog Chris Guerra made Justin's life hell ... following and chasing him at every opportunity.

The sources claim Chris flat-out lied when he called a friend shortly before he was killed, claiming he saw Justin smoking pot in a pipe while driving his Ferrari earlier that day. The sources say multiple witnesses will say the only time Justin left the Four Seasons on New Year's Day was to go to Roscoe's Chicken and Waffles in Hollywood for lunch, and there was never a pipe in sight.

Sources connected to Justin and Selena say the photog was lying when he told the friend he saw a car belonging to Selena Gomez on the Four Seasons property. The sources tell us ... the two of them flew to Mexico for New Year's Eve, but had a blow-out argument on December 30 and broke up. Selena left Mexico that same day and Justin left for L.A. on the 31st. They haven't seen each other since and she was never at the Four Seasons on New Year's Day.