Men who assault their partners are mentally ill.
Woman abuse is too widespread to be explained away by mental illness. Most men who assault their partners confine their violence to the privacy of their home. The abuse is often directed to particular parts of the body that will not visibly bruise. Obvious restraint and forethought is necessary to accomplish this. Violent husbands are not likely to attack their bosses when frustrated. If the man was truly mentally ill, he would lack the ability to be selective in his targets and controlled in his administration of abuse.