Car A was making a right turn headed north out of a Dunkin Donuts onto 4 lane (2 in each direction) road in the far right lane. Car B is in left lane (also headed north) signalling to make a left turn into hotel parking lot. Car C is behind Car B and changes lane into the far right lane while car A is turning onto road. Collision between A and C. Whose fault?

Car A is at fault, they would be charged with * at least where I was a officer** with failure to yield right of way or making an improper right hand turn.

Does not matter that car C changed lanes, does not matter that Car A did not see them, Car A can not make a turn into traffic unless it is clear,

I agree with the Father. The car on the main road has the right of way, and the car in the parking lot needs to be sure that they can safely enter the road before doing so.

** I will add I have years of law enforcement and have had several advanced accident investigation classes. My answers are based on laws as they were in Georgia about 5 years ago. *** but of course most accident liablity laws are very similar between states, esp on a accident like this.