There’s a four-way intersection controlled by a traffic light. The main road (let’s call it Main St.) is one lane each way with a central turning lane, the crossing road (let’s call it Cross St.) is one lane each way. Main St. has the green light, and left turns are allowed on green after yielding to opposing traffic.
There’s a car in the right “through” lane on Main St. attempting to turn left onto Cross St. (which is illegal, but I see this all the time). While the turning car is waiting for the traffic to clear on the opposing lane so they can make their turn, a driver behind the turning car gets impatient and decides to pass through the intersection by using the central turn lane (which is also illegal, for obvious reasons). The opposing traffic clears and the turning car starts their turn just as the second car is reaching the intersection in the central turn lane and they collide.
Who is most at fault?