The NY Times asks a medical ethicist on the issue:

In general, patients may decline medical treatment if they are informed of the consequences of doing so and capable of making such a decision.

“There are special considerations in emergency medicine because of the need to make rapid assessments,” Ms. Berlinger said. “You could have an evident life-threatening injury “” someone bleeding out of a carotid artery “” or the potential for a life-threatening injury that you can’t see, such as a stroke or spinal-cord injury. It is not always clear what is the patient’s capacity to make decisions, especially if the doctor suspects a head injury.”

A jury or judge evaluating the case, Ms. Berlinger said, might have to answer these questions about the procedure: “Was it medically necessary? Was the patient capable of understanding what was going on and making a decision about it and understanding the consequences of refusal?”

The area of contention lies in when exactly is one “capable of making an informed decision”. To some, it may simply be an ability to coherently answer questions. However, the answer is not so clear-cut in cases of head trauma. There is some subjectivity in the issue, which is why this lawsuit exists in the first place.

Personally, I think the case is frivolous. But I understand that it is impossible for non-medical personnel to be aware of the nuances of a head trauma workup, hence the outrage. Which is why having physicians communicate to the public why we do the things we do is important. You can read perspectives from both sides here.