An attempt to impeach or overturn a judgment rendered in a judicial proceeding, made in a proceeding other than within the original action or an appeal from it.
A defendant may make a collateral attack on a judgment entered against him or her in some instances. If a default judgment is entered against the person, he or she may collaterally attack the authority of the issuing court to render it, claiming that there was a lack of Personal Jurisdiction.
Similarly, if a man leaves his wife and moves to another state where he obtains a Divorce that contains no support provisions for the woman, she may directly attack the judgment by appealing it in the state where it was entered or initiate a collateral attack by bringing her own divorce action in her state of residence.
A collateral attack may also be made upon a judicial proceeding in a single state.
n. a legal action to challenge a ruling in another case. For example, Joe Parenti has been ordered to pay child support in a divorce case, but he then files another lawsuit trying to prove a claim that he is not the father of the child. A "direct attack" would have been to raise the issue of parenthood in the divorce action.