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Why may a defense lawyer not knowingly present perjured testimony?

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illustration from Charles Dickens's Bleak House — Legal ethics Illustration by Hablot Knight Browne for Charles Dickens's *Bleak House*. Here Lady Dedlock is visited by her cunning old lawyer, who discovers her deepest secret and threatens to reveal it to her husband.

A defense lawyer is ethically prohibited from knowingly presenting perjured testimony because they are considered an officer of the court with a fundamental responsibility to uphold the integrity of the legal system.1

While a lawyer is obligated to advocate zealously for their client, this duty does not extend to using dishonest tactics. The legal profession maintains that a lawyer must eschew methods that would defeat the fair administration of justice. Consequently, an attorney may not deliberately resort to perjured or other false testimony.12

This ethical stance is rooted in the principle that the lawyer’s role is to assist the court in reaching a just outcome rather than to manipulate the truth. By refusing to present false evidence, the lawyer ensures they do not misstate facts or undermine the legal process, thereby maintaining their professional duty to both the client and the public interest.13