Although we do not know for sure what causes domestic violence (in New Jersey or anywhere else) the general consensus among scholars is that domestic violence is a learned behavior that is reinforced by societal factors. In other words, it is not caused by mental illness or alcohol abuse but, rather, by choices men make and the ways they are socialized.
It is generally believed that domestic violence is caused by the desire on the part of men to control their partners. It is believed that men see women as subordinate to them and wish to control them. They see violence as a way to accomplish this.
Scholars tend to believe that this is caused by our societal values. It is caused by the idea that men are more important than women and that men should be in control of society and of their relationships. This attitude has been blamed on a variety of factors, everything from religion to pornography.
It is, of course, not clear why some men act on such impulses and others do not. However, scholars believe that many factors in our society teach men that they are superior to women and that women are objects for them to control. This, along with laws that do not tend to protect women from violence very well, lead to domestic violence.