Causation is one of the key elements that you must prove if you are to prevail in a negligence-based lawsuit for personal injury under Ohio law. There are two kinds of causation: direct, and indirect. For our purposes we will focus on the type of cause that is important from a legal point of view, which is direct or "proximate" causation.
It may be helpful to think of proximate cause as a way to limit the scope of possible causes of injury by requiring the cause of injury to be directly traceable to the wrongful action of the defendant. Another way to express proximate cause is through the "but for" rule: but for the direct and uninterrupted consequences of the defendant's act, the plaintiff's harm would not have occurred.
The determination of proximate cause is an exercise in foreseeability: the harm must have been something that could have been reasonably anticipated or expected from the actions of the defendant and the plaintiff under the circumstances at the time. There can be multiple proximate causes, and multiple defendants, in a negligence lawsuit: for example, if in a chain rear-end collision involving three cars one driver drove too fast and rear-ended another in a second car, who in turn was following the third car ahead of him too closely and struck it, both of these drivers may be proximately responsible for the harm to the plaintiff in the third car.
Identifying proximate causes for your injury in a car accident or other negligence-based event is one of the tasks of your personal injury attorney, who will work with you to assess the facts of your case to determine all of the possible direct causes of harm and the parties responsible.