Whose fault it is depends on a lot of variables, and only the ICBC claims adjustor can determine the fault for each particular circumstance. Pay attention to the traffic control devices and which car was legally required to yield to the other, regardless of the turn indicators. In other words, whose fault would it be? Maybe YOURS.
Turn signals are nice, and we are legally required to use them before turning, but, you should never trust that just because a car has a turn signal, that it will actually turn.
The rules of the road do not say anything about how a turn signal can be your guarantee to take the right of way (in fact, quite the opposite is true.)
In this classic example, Car 1 is signalling for a right turn, but he’s not actually turning right. Car 2 wants to go left. If Car 2 turns left, and Car 1 crashes into it, the fault will be probably on car #2, although may be shared. Car 2 is the one facing a stop sign. Cars at stop signs are legally required to yield to cars that don’t have stop signs (Car 1). The fact that the car had a signal, but didn’t turn, may not stand up in the court of law. Yes, it’s annoying, dangerous, and frustrating; but it’s no good reason to sacrifice your safety. The best thing to do is simply wait and make sure the right turning car is actually turning.
Try to avoid thinking of things in terms of “Who’s fault would it be?” Rather, try to think of ways that everybody can keep the roads safer by being more defensive, and preventing collisions before they happen in the first place, so that we don’t have to deal with the ugly aftermath.