According to USLegal, the criteria that determines an unfit parent varies by state. In general, the parent in question is legally unable to retain parental rights due to abuse, negligence or an inability to accept the responsibility of a dependent minor (as in the case of mental instability).
Minella Law Group states that the deciding of custody is a direct effect of a fitness hearing or a child custody evaluation. For example, California courts determine fitness, and thereby custody, by evaluating 10 areas of parental behavior both current and past. These are:
- Age-appropriate limitations wherein the parent only allows activities that are in context with the child's age
- The parent's ability to recognize the child's needs and respond in an appropriate and timely fashion
- The parent's history of providing care for the child
- The parent's history of cooperating with the child's other parent to provide appropriate care
- The parent's history of child abuse with this child or other children
- The parent's physically or emotionally abusive behavior towards the other parent particularly in front of the child
- The use of illegal drugs or the abuse of alcohol or prescriptions drugs
- The parent's social adjustment
- The child's comfort and feelings towards the parent
USLegal explains that some U.S. states require fitness hearings and a period of time in which the parent is allowed to correct the problem prior to terminating parental rights. Abandonment, whether in terms of support or the actual physical abandonment of a child, and incarceration can be cause for finding a parent unfit.