Unclean Hands

Unclean Hands refers to the legal doctrine that stops a plaintiff who has acted unethically in the past in regard to a lawsuit from winning the new suit or from possibly recovering as much money as the plaintiff would have if he/she had behaved honorably.

Additional Sources

FindLaw

An equitable doctrine: a complainant will be denied relief if he or she has engaged in misconduct (as acting in bad faith) directly relating to the complaint

The condition of having engaged in such misconduct and being barred from equitable relief.

The Free (Legal) Dictionary

n. a legal doctrine which is a defense to a complaint, which states that a party who is asking for a judgment cannot have the help of the court if he/she has done anything unethical in relation to the subject of the lawsuit. Thus, if a defendant can show the plaintiff had "unclean hands," the plaintiff's complaint will be dismissed or the plaintiff will be denied judgment. Unclean hands is a common "affirmative defense" pleaded by defendants, which must be proved by the defendant. Example: Hank Hardnose sues Grace Goodenough for breach of contract for failure to pay the full amount for construction of an addition to her house which she admits. The court denies any relief to Hardnose when Goodenough proves that Hardnose had shown her faked estimates from subcontractors to justify his original bid to Goodenough.

Wikipedia

Unclean hands, sometimes clean hands doctrine or dirty hands doctrine is an equitable defense in which the defendant argues that the plaintiff is not entitled to obtain an equitable remedy on account of the fact that the plaintiff is acting unethically or has acted in bad faith with respect to the subject of the complaint—that is, with "unclean hands". The defendant has the burden of proof to show the plaintiff is not acting in good faith. The doctrine is often stated as "those seeking equity must do equity" or "equity must come with clean hands".

A defendant's unclean hands can also be claimed and proven by the plaintiff to claim other equitable remedies and to prevent that defendant from asserting equitable affirmative defenses. In other words, 'unclean hands' can be used offensively by the plaintiff as well as defensively by the defendant. Historically, the doctrine of unclean hands can be traced as far back as the Fourth Lateran Council