Judge Fitzsimmons served as an Assistant Cuyahoga County Prosecutor (from 1977-1980).  In 1980, she was the first woman appointed as Special Attorney in the U.S. Department of Justice, Organized Crime Strike Force in Cleveland.  Her most notable case was as the lead prosecutor in United States v. Lonardo, Gallo, et al, a three-month trial in federal court which resulted in the conviction of former Cleveland Mafia boss Angelo Lonardo and five of his subordinates in 1983.

The Lonardo case gained national attention because the lives of the FBI case agents were threatened during the investigation, resulting in the relocation of their families.  Death threats were made to Donna Congeni Fitzsimmons and her family during the course of the trial.  The Justice Department successfully prosecuted the perpetrators of such threats at the conclusion of the Lonardo prosecution.  Judge Fitzsimmons received special commendations from the Director of the Federal Bureau of Investigation and the United States Attorney General.

Based upon her work in that case, Judge Fitzsimmons was appointed Deputy Counsel to President Reagan’s Commission on Organized Crime in Washington, D.C. from 1984 to 1985.  She then entered private practice as a partner at Arter & Hadden for eight years, specializing in the defense of medical malpractice and medical product liability claims.

Soon after taking the bench, Judge Fitzsimmons dedicated herself to improving the delivery of justice in cases that involved intimate partner offenses, including domestic violence and stalking.

She created the Stalking Victim Support Group and a training course for law enforcement officers, probation officers, and court personnel involved in handling stalking cases.  Judge Fitzsimmons’ teaching experience includes courses presented to her judicial peers, law enforcement personnel, and lawyers.

In February of l997 through 2008, Judge Fitzsimmons was appointed as the Municipal Court representative to the Cuyahoga County Criminal Justice Supervisory Services Board, and the Executive Committee to that Board.  This Board oversees the expenditure of federal and state funds for criminal justice programs.  From February 1997 through the present she has served as Chair of the Cuyahoga County Violence Against Women Act Committee.

In March 1997, Judge Fitzsimmons was selected by the Junior League in honor of their 85th Anniversary as a “GEM” of Cleveland, based on civic service in furtherance of the cause of women. In April 1997, she was appointed to the Board of Trustees of the Northeast Ohio Leukemia and Lymphoma Society—and presently continues to serve on that Board.  In June 1998, Judge Fitzsimmons was appointed to the Ohio Supreme Court Security Committee, and in January 2001 to the Ohio Supreme Court Criminal Procedure Committee. Most recently she has served on the Supreme Court Jury Committee and the Ohio Municipal Judges Association Committees on Ethics and Specialized Dockets.  She is a Life Member of the Eighth District Judicial Conference.

Judge Fitzsimmons served as a trustee of Community Challenge from 1997 through 2003 and was appointed to the Fairview Hospital Community Advisory Board in 2003 through the present.  In 2010 Judge Fitzsimmons proudly sang in the Sing-Out Choir, a benefit for the Cleveland Rape Crisis Center.