General signs to help identify potentially abusive partners:
Jealousy: Do they become angry when their partner talks to someone of the opposite sex?
Isolation: Do they want to know where their partner is at all times or isolate their partner from friends and family?
Aggression: Does their anger draw fear from their partner?
Control: Do they act as though their partner belongs to them?
Extreme mood changes: Do they act like two different people?
Substance abuse of alcohol and/or drugs.
Source: Sojourner House Domestic Violence Program