In the run-up to trial, my complaining witness discloses information that is clearly Brady. The nature of the information is embarrassing to the witness and will expose the witness to public humiliation and derision. I choose to dismiss the case with a proviso that it will never again be filed. I do not disclose to the opposing party the information. Have I violated a disciplinary rule or canon of ethics?

You have a duty to disclose exculpatory or mitigating evidence to assist the defendant prepare for a TRIAL. Having sidestepped the need for a trial, your constitutional duty is avoided.

Now, that doesn't necessarily address your ethical duty. Disciplinary rules don't necessarily track constitutional obligations. They can sometimes be broader or involve different obligations.

Texas Disciplinary Rule 3.09 requires a prosecutor to make timely disclosure of all evidence that tends to negate guilt or mitigate the offense. The Rule, speaking of "timely" disclosure, seems to reflect the constitutional obligation of helping a defendant prepare for some event before it happens. That would be the trial.

So, seems to me you have resolved your ethical duty by avoiding the trial.

A couple of years ago, the US Supreme Court, in a case called Ruiz, approved a prosecutor's refusal to disclose potential impeachment material when a defendant accepted an offer to plead guilty and receive a negotiated sentence. The SC indicated that the plea of guilty avoided the trial, waiving any right to the impeachment material.

The SC expressly left open the question of whether the outcome would be same regarding evidence of innocence.

Thanks, JB, for the answer and the article.

Is the defendant going to feel cheated by the fact that he got his case dismissed without the chance to go to trial with the Brady material. Seems to me once you say I'm dismissing your case, most defendants don't care why, they just want to go home.