The definition of an unfit mother involves multiple factors, such as the inability to understand and provide for a child's needs and any history of child abuse, domestic violence or substance abuse. These factors are weighed by a court in order to determine maternal fitness.
One commonly used determinant of an unfit mother is the absence of limits appropriate to the child's age. A kindergarten student permitted to watch R-rated movies or cable television programs with adult content, or a teenager with no curfew, may indicate a lack of appropriate limits.
If the mother has a history of child abuse, with the child in question or any other, she may be considered unfit. A mother who has been emotionally or physically abusive to the other parent, or has issues with prescription or illegal drugs or alcohol, may also be considered unfit. Psychiatric illness or an incapacity to function normally in society can also determine an unfit mother.
The court's decision may rest on a more subjective critique. A general lack of responsiveness to the needs of the child is considered a sign that a mother may not be fit. A final factor that courts may consider, depending on the age of the child, is the attitude the child expresses about the mother.