IOWA CITY — A supervisor in the Iowa public defender’s office quit his longtime side job as a police officer after critics said his dual roles created a conflict of interest, according to a resignation letter released Friday.

Mike Adams, supervisor of the special defense unit, resigned “with great sadness” from the Colfax Police Department, according to the Oct. 8 letter released to The Associated Press under the open records law.

“I want to thank you for giving me the opportunity to serve the citizens of Colfax and Jasper County in one of the most noble professions, and in the company of some of the finest people I will ever know,” Adams wrote to Colfax Police Chief Andy Summy. “I will forever cherish my experiences and my first responder family.”

His resignation came weeks after the AP reported on concerns about Adams’ side work in law enforcement in a jurisdiction where his unit routinely represents low-income defendants charged with serious crimes.

Several defense lawyers criticized the arrangement as a conflict of interest, with one comparing it to the “fox guarding the hen house.” Tricia Bushnell, director of the Midwest Innocence Project, said Adams’ side job potentially undermined his relationship with clients who would not feel comfortable alleging police misconduct.

“It raises a number of potential conflicts, including the appearance of impropriety, where the appearance alone is enough to dictate that it should not be the practice,” she said.

For days, Adams has ignored questions about whether he resigned from Colfax, where he had been a part-time reserve officer since 2008. City records indicated that he typically worked hundreds of hours per year, usually as an unpaid volunteer. Adams, who earned $122,000 in his state job last year, didn’t return messages Friday.

Adams had contended that he did not have a conflict of interest because he did not personally represent defendants charged in Jasper County, which includes Colfax. He argued that his work as a police officer made him a better public defender.

He told his bosses in August that questions about his work for Colfax were “no big deal” and incorrectly suggested they were being spread by a former employee, according to emails obtained by AP.

His dual roles became a problem when he arrested David Hawkins on a felony burglary charge in August. He told his public defender colleagues they could not represent Hawkins “due to a conflict with a state’s witness,” but without mentioning he was the arresting officer.

Hawkins was a potential witness in a murder case involving Jeffrey Stendrup, who is charged in the 2018 beating death of a man in Colfax. Lawyers from Adams’ unit were defending Stendrup, even though the Colfax Police Department helped investigate the case.

Adams pledged not to access any files related to the case at either of his jobs and vowed to approve any expenses his subordinates sought for Stendrup’s defense.

But Stendrup’s lawyers nonetheless determined they had a conflict.