When can you have a person declared legally dead?

You can declare a person officially dead when a doctor or medical examiner for a mortuary says the person is dead.  Just because someone is missing, does not mean that they are declared dead.  Indeed, many times, people try to make it look like they are dead to avoid creditors, police enforcement agencies or other people and they try to start new lives in new cities/countries.  In this case, being missing for 4 years is a long time, and there may be an issue as to whether the husband died in the car crash, however, for purposes of actually declaring the person dead, there is no basis to do so unless the body is found or it is determined by a doctor/medical examiner that the person is dead and the body cannot be located. 

In attempting to determine whether a missing person has died there is a legal presumption that they are alive until proved dead.  Where evidence indicates that the absent person was subject to a particular peril, he or she will be legally presumed dead after 7 years; this time period may be shortened if the state enacts legislation changing it.  For instance, in the case of persons missing as a result of 9/11, several states legally provided that a person need to only have been missing for a matter of months.  In no event will a courtmake the assumption that a missing person is dead unless it is reasonable to assume so; a person will not be declared legally dead without proof that an honest and complete search was made for him or her.

Based on your facts, having your husband declared legally dead may be problematic.  For one thing, he has been missing for only 4 years not enough time, I believe, under NC law.  Also, you haven't indicated what, if any, investigation/search has been done.  Finally, while there was a peril involved (crashing his car into a river), there was also a reason that your husband would not return home if still alive - he would have faced charges for his assault upon you.  Without knowing more specifics of your situation it's hard to say more.  At this point you would need to consult directly with an attorney in your jurisdiction as to all of this.