The Hennepin County chief public defender resigned Monday afternoon amid a federal investigation into allegations of tax evasion.

Kassius Benson sent emails to staff and State Public Defender Bill Ward announcing his resignation two months after news broke of the investigation. The resignation is effective Oct. 24, but he said in the email that he will take personal time off until then. In the notice sent to Ward, Benson expressed his gratitude for having led the office for the past two years.

"I know that I have served the position of Chief well," Benson wrote. But he said that "personal issues involving matters outside of my position … will likely distract from the great work that we have accomplished."

He signed off his notice to Ward by saying that he "will forever be indebted to the public defender system for its influence in my development as a trial attorney and attorney of conscience. My commitment to this work will simply continue in a different capacity."

In an email to the Star Tribune, Benson confirmed that he provided a notice of resignation and forwarded it to Ward on Monday afternoon.

"The email is my comment on the resignation at this time," he said.

Ward wrote in an email to the Star Tribune that he and Benson met over the weekend and discussed his decision to resign. "It is a private, personal decision for Mr. Benson. I am personally sad to see him resign but I completely respect his resolve."

Ward credited Benson and his leadership team for developing a training and development program for attorneys. He also said that Benson increased diversity among staff and management ranks, from less than 10% when he was appointed to nearly 50% today.

"Mr. Benson should, rightfully, be proud of the work he has accomplished on behalf of the indigent accused," Ward wrote.

Bob Kolstad, who has been the public defenders' union steward since 2016 and with the office since 2010, said that while many young lawyers who looked up to Benson as a mentor will be sad to see him go, many lawyers already have left under Benson.

"I haven't seen the morale in our office any lower," Kolstad said. "I don't think you can note that without laying that at the foot of management. I don't think people feel supported in the struggles they have with judges. They're overworked. They have too many cases and there is no real person for them to turn to for support."

The union recently cast a vote of no confidence in Ward, but the Board of Public Defense reappointed him last month.

Ward previously told the Star Tribune that he was unaware of the federal investigation into Benson before hiring him to lead the state's largest public defender office in January 2021.

In August, it became public knowledge that Benson was under investigation into whether he failed to pay federal taxes withheld for employees at his private Minneapolis-based criminal defense firm, Kassius Benson Law.

As the sole shareholder at his firm, Benson was responsible for the collection and payment of employment taxes and filing the appropriate quarterly IRS forms. He employed at least five people in 2013 and again from 2015-2019 and failed to file proper quarterly forms and turn over $159,262 in taxes he withheld during that stretch, the affidavit said. The warrant, issued in January, was under seal until July.

The federal affidavit, initially filed under seal, sought access to servers containing payroll records from Benson's firm dating to 2013.

The federal probe started in July 2020 — six months before Benson was hired by the state — when, according to the affidavit, revenue agent Joni Jacobsson began an audit relating to the 2017 forms Benson was to have filed. The agent expanded the investigation to 2013 and 2015-2019 on finding that Benson had failed to pay employment and unemployment taxes and to file the forms.

Benson paid gross wages of $710,079, but withheld $159,262 in total employment taxes from his employees and failed to turn over the money to the government, the affidavit said.

By January 2021, Benson had stopped speaking to Jacobsson. While he paid all taxes and filed the appropriate forms for 2020, he did not file the forms or pay taxes for 2013 and 2015-2019. He reported no employees in 2014 and didn't issue any W-2 forms.

A former employee of Benson's private firm told the Star Tribune that they testified in July under subpoena before a federal grand jury.

He is the second leader of the Hennepin County Public Defenders Office to leave in as many years. Mary Moriarty was suspended as chief public defender in 2019 after five years on the job, then the state board declined to reappoint her.

Benson replaced Moriarty, who is running to become the next Hennepin County Attorney. She won a $300,000 settlement for what she said was to avoid a looming discrimination lawsuit over her advocating for pay parity.

Kolstad said that lawyers would like to have input into the process of deciding who becomes the interim chief and, ultimately, Benson's replacement.

"I think this whole thing shows that there is a lack of concern for the people who work in our office," he said.

Star Tribune staff writer Rochelle Olson contributed to this report.