Blood test from an accident victim while unconscious or serious head trama?

The officer doesn't take blood -- it is usually a medical professional team (EMT, doctor, nurse).  Since blood is like fingerprinting (i.e., not testimony), an officer or detective may be able to obtain it based on the urgency of the issue (drugs in the system), possible criminal scene, and depending on certain type of request, a search warrant may be allowed.

If a blood draw is necessary, usually doctors will send to the lab and police can simply subpoena the results.  Or, depending on what the victim did (depending on the situation), the police can arrest upon release of the patient and have jail nurse to draw blood.  In a head trauma, I can see blood being drawn and sent to the lab.

Further, many states actually make it a violation of law for a physician, nurse, medical perosnnel to refuse to draw blood or obtain certain samples based on police request except in unusual circumstances.

The Supreme Court confirmed the constitutionality of laws that permit police to obtain blood for testing, with the help of a doctor, in the 1966 case Schmerber v. California. The suspected drunken driver refused testing in Schmerber. But the court's ruling turned on the limits of the patient's right against self-incrimination. So, the high court has never considered whether medical ethics or the doctor-patient relationship should preclude a physician's involvement in testing that a patient doesn't need.

Let's assume this happened in North Carolina:

http://www.helium.com/items/1254614-legal-advice-getting-a-dui-in-north-carolina

Most states do allow for blood to be taken under these circumstances.  While it may not seem fair to you most courts have found that this is neither a violation against an individual's right against self-incrimination or a violation of their right to due process.

Specifically, North Carolina has an "implied consent" law.  This means that you agree to submit to a chemical test of your blood, breath or urine if an officer of the laws suspects that you are driving while intoxicated. If you refuse such a test your drivers license will be immediately suspended for 30 days followed by a hearing in which the court could suspend your drivers license for an additional 12 months.

I realize that if the individual were conscious he still could have refused (although there would have been fines and penalties),  yet while unconscious he was not able to so refuse.

While tt does appear that the officer was well within his right to take a blood sample such as this you may just want to check  further since I'm not a praticing attorney in North Carolina.  Try calling the DMV or possibly the Public Defender's office just to make sure.