If you'd collided with the pedestrian, there might well have been sufficient evidence to justify a charge of 'driving without due care and attention' against you. You're expected to remain vigilant about possible hazards in your path, so you're definitely expected to check what's to your left before turning in that direction. (I assume that the pedestrian you refer to was an adult but you need to be looking out for children, who might be more likely to step into traffic, as well).
However in a civil case (if you'd hit the pedestrian), it's likely that a court would rule than an (adult) pedestrian stepping into the path of your vehicle was partly to blame for the accident.