In a divorce case, the attorney knowingly allows his client to commit perjury
<p>What kind of accountability is the attorney subject to?</p>

<p>Taking Washington state as a representative example, the <a href="https://app.leg.wa.gov/rcw/default.aspx?cite=2.48&amp;full=true" rel="nofollow noreferrer">State Bar Act</a> empowers the board of governors of the state bar association to set rules and penalties for the practice of law. This includes the power to disbar a member, and there are specific rules (2.48.220) pertaining to suspension and disbarment, which includes (11) Violation of the ethics of the profession. 2.48.230 then says that "The code of ethics of the American Bar Association shall be the standard of ethics for the members of the bar of this state". </p>

<p><a href="https://www.americanbar.org/groups/professional_responsibility/publications/model_rules_of_professional_conduct/rule_3_3_candor_toward_the_tribunal/" rel="nofollow noreferrer">ABA rule 3.3(b)</a> states that </p>

<blockquote>
  <p>A lawyer who represents a client in an adjudicative proceeding and who
  knows that a person intends to engage, is engaging or has engaged in
  criminal or fraudulent conduct related to the proceeding shall take
  reasonable remedial measures, including, if necessary, disclosure to
  the tribunal.</p>
</blockquote>

<p>If an attorney knows (not just thinks, actually knows) that the testimony is perjurious, he should persuade the client to not do so, or should seek to withdraw from the case. The ABA <a href="https://www.americanbar.org/content/dam/aba/publications/criminaljustice/wcc_newsletter_unlawful_conduct.authcheckdam.pdf" rel="nofollow noreferrer">guidance on this</a> (p. 9) observes that an approach sanction by some courts is</p>

<blockquote>
  <p>to allow the client’s testimony under the narrative approach (i.e.,
  allowing the client to  narrate instead of asking any questions).
  Lawyers who take this approach should not adopt or  rely  on any
  perjured testimony later in the trial.</p>
</blockquote>

<p>I will assume that you refer to some jurisdiction in the U.S. My answer is purely theoretical, in part because judges give lawyers too much leeway for acts which are in furtherance of the obstruction of justice.</p>

<blockquote>
  <p>What kind of accountability is the attorney subject to?</p>
</blockquote>

<p>That could warrant sanctions against him for partaking in the concealment --or assistance thereto-- of "<em>material having potential evidentiary value</em>" (see Rule 8.4(a) of <a href="https://courts.michigan.gov/Courts/MichiganSupremeCourt/rules/Documents/Michigan%20Rules%20of%20Professional%20Conduct.pdf" rel="nofollow noreferrer">Michigan Rules of "Professional" Conduct</a>, double quotes added). Any disciplinary sanctions this might elicit is totally independent of the litigation where the misconduct occurred.</p>

<p>Regarding the underlying litigation, the misconduct might defeat the <em>attorney-client</em> privilege on grounds of the <em>crime-fraud</em> exception to that privilege. Additionally, the opposing party may want to consider a motion seeking the disqualification of the attorney from the case, but I am not aware of whether this is pursued/achieved.</p>

<p>It is noteworthy, though, that the confidentiality of attorney-client communications makes it very difficult to <em>prove</em> that the attorney <em>knew</em> that his client was committing perjury. You can also expect from the lawyer a repertoire of vexatious allegations to deny his abetting of perjury.</p>

perjury