One of the most challenging elements of a medical malpractice claim is proving causation. Malpractice laws in Ohio say that plaintiffs must prove two things: that the defendant did not adhere to a generally accepted standard of medical care, and that this negligence led to the injuries in question. It is that second step that can make or break a case.
The reason is that some injuries can result even where there is negligence on the doctor's part. For example, almost any surgical procedure comes with foreseeable side effects. The surgeon may have been negligent, and the patient may have developed these complications, but correlation does not imply causation.