Who is at fault if someone drives through an intersection and hits a vehicle?

It depends on what kind of intersection is is and directions the cars were coming. The rules of the road determine who has the right of way. However, the person with the "last clear chance" to avoid a collision is almost always the one found to be "at fault." You can't simply crash into someone because they're breaking the law, if you can avoid it. For example: If you have the right-of-way to make a left hand turn in that intersection and person hits you, then it's their fault. If you have the green light to go straight through and the other car is making a left hand turn in the intersection (that car is suppose to wait for you to go through) then it's their fault. Usually the police are brought into it and they can often determine whose fault it was. However, the courts may ultimately decide liability, based upon the facts put into evidence, so get names of any witnesses and take pictures if you think it's not your fault.