A federal prosecutor who had a secret romance with a married FBI agent has been barred from practicing law for six months after the Louisiana Supreme Court found she committed professional misconduct.

Assistant U.S. Attorney Mignonne Griffing of the U.S. Attorney's Office for the Western District of Louisiana in Shreveport failed to tell her bosses or defense counsel in two high-profile public corruption cases about her love interests with the FBI agent, who testified in her cases. When the affair came to light, she was dishonest or misled then-U.S. Attorney Stephanie Finley about the relationship, according to court documents in the attorney disciplinary case.

“Respondent's personal interest in keeping quiet her relationship with the FBI agent deprived her client, the United States through her superiors, of information they needed to make informed decisions relative to the representation of the government and disclosure obligations to defendants,” the ruling said.

The Louisiana Supreme Court on Oct. 18 suspended Griffing from practicing law for one year and one day, but deferred half of the sentence, which means Griffing's actual suspension will run six months. She'll then face one year of unsupervised probation and have to complete 40 hours of continuing legal education in ethics and professionalism, according to the Louisiana Supreme Court's per curiam ruling in In Re C. Mignonne Griffing.

Griffing didn't return a call seeking comment before deadline, and neither did her lawyer, Leslie Schiff of Schiff, Scheckman & White in Opelousas, Louisiana.

Griffing has been a federal prosecutor since 1990 and most recently prosecuted white collar crime and public corruption cases, according to the ruling. She became involved in an intimate, romantic relationship with an FBI agent who led the investigations into many of her cases. He didn't always testify at trial, but he often testified before grand juries and in other hearings that Griffing handled. Griffing and the agent kept their relationship confidential because he was married.

The agent was lead investigator in two of Griffing's big public corruption cases involving two city councilmen in Monroe and the sheriff in Ouachita Parish.

Although the court noted that there was no evidence that the agent's testimony was untruthful nor that the relationship affected his testimony, the court took particular issue with Griffing's case against the sheriff. In that matter, Griffing had allegedly agreed with the sheriff's lawyer, Marty Stroud, that if the sheriff were indicted, he would be allowed to self-surrender. She later learned, however, that the sheriff was talking to others about her relationship with the FBI agent, according to the decision. She then called Stroud and threatened to have the sheriff publicly arrested if he didn't stop making such statements. The sheriff subsequently was indicted and arrested, handcuffed and led away by law enforcement. The sheriff later fired Stroud as counsel.

Stroud didn't return a call seeking comment before deadline.

Eventually, the U.S. Attorney's Office learned from Stroud about Griffing's relationship. When the office questioned her about it, she falsely denied or misled the U.S. attorney at first, but later told the truth to the first assistant U.S. attorney. She was suspended without pay for 19 days and returned to work as an appellate attorney.

Alexander Van Hook, formerly the first assistant but now the acting U.S. Attorney for the Western District of Louisiana, didn't return a call seeking comment before deadline.

Louisiana's Office of the Disciplinary Counsel alleged that Griffing's misconduct had violated rules that: prohibit an attorney with a conflict from representing a client; require a prosecutor to disclose exculpatory or mitigating evidence to the defense; prohibit a lawyer from engaging in conduct that prejudices the administration of justice; and prohibit a lawyer from dishonest, fraudulent, deceitful or misrepresentative conduct.

During the disciplinary case, Griffing admitted her relationship with the agent, and the fact that she had a duty to disclose the relationship to the U.S. attorney and the defendants. She denied that there was a conflict of interest though, and she denied that she committed misconduct in having the sheriff arrested.

Griffing's behavior caused the U.S. attorney's office's to lose respect and confidence in Monroe, said the ruling. She also hurt Stroud's business and professional reputation. The situation might even harm other cases if someone raises the relationship issue again.

The Louisiana Supreme Court took up the matter after the Louisiana State Bar Association's Office of the Disciplinary Counsel appealed lower decisions by a disciplinary committee and disciplinary board, which were planning to defer all of Griffing's suspension.

Louisiana Chief Disciplinary Counsel Charles Plattsmier didn't return a call seeking comment before deadline.

Considering Griffin's multiple rule violations and especially her dishonesty and misrepresentation, the high court decided that she must serve an actual period of suspension.

“We have not previously had the opportunity to address directly the misconduct of a government prosecutor who maintained an intimate or romantic relationship with a law enforcement agent called as a witness,” the court wrote. “However, we have repeatedly held that public officials—and prosecutors in particular—are held to a higher standard than ordinary attorneys.”

For more details on the case, see The Ouachita Citizen's report of Griffing's three-day, 15-witness attorney disciplinary hearing.

Follow Angela Morris on Twitter: @AMorrisReports