A trial lawyer and licensed psychologist, Costello focuses on litigation, dispute resolution and appeals at Dykema Gossett PLLC, where she is in charge of pro bono services. As the pro bono manager, Costello is responsible for overseeing approximately 45 cases that her firms' attorneys and summer associates take on each year. Dykema Gossett takes responsibility for three clinics annually composed primarily of Legal Aid and Defender Association of Detroit clients.

Costello's longstanding commitment in directly providing free legal services to low-income clients, and leadership in setting up organizational and administrative support is well known. She has devoted generous amounts of her time to Community Legal Resources and to programs like the First Step Legal Advocacy Project, helping victims of domestic violence. At the same time, she educates attorneys statewide on the unique aspects of lawyering on behalf of domestic violence survivors. She was an integral part of the State Bar's Open Justice Pro Bono Project for Domestic Violence Victims statewide attorney training last year.

Those who know Costello describe her commitment to deliver quality services to clients who could not otherwise afford representation as inspiring and outstanding. She has been described as a lawyer who demonstrates her commitment by her actions by often taking on pro bono projects herself when members of her staff are unavailable to help.

Margaret Costello is a graduate of Pennsylvania State University. She received her law degree from the Detroit College of Law. She sits on the board of directors of the Detroit Metropolitan Bar Association and is a member of the State Bar of Michigan's Representative Assembly. She is chair of the Assembly Review Committee and a member of the Pro Bono Involvement Committee.