Is lying under oath a justifiable tactic in the adversary system?

Students should clearly understand that the adversary system does not justify lying in court. Neither does it eliminate gross exaggeration, lies, or deliberately misleading the questioner.
Lying by witnesses under oath about a material fact is the crime of perjury. Nevertheless, parties and witnesses routinely exaggerate to the point of lying, and in the overwhelming number of circumstances no perjury charges are instigated. Rough and tumble trial lawyers long ago coined the phrase "testifying under oath.".
Students should be able to draw analogies to political rhetoric, and to distinguish between testimony by professionals to, for example, Congress, and testimony by a lay person in court. Under the adversary system, every person pleads "not guilty" (i.e. "I did not shoot the deceased.".).
Technically, those who are found guilty have committed perjury, but perjury charges are never brought in addition to the underlying crime.
If an attorneys lies in court, it raises an ethical question, at the very least. It could be rounds for a contempt of court charge. On the other hand, the adversary system does encourage the aggressive presentation by opposing attorneys of every conceivable applicable theory, factual interpretation, and citation of relevant statutes or common law rules. This exaggeration is to be expected.