Skip to main content


Not yet reviewed

About me

A shareholder and managing partner of Brennan Steil S.C., Duffy is a litigator whose practice focuses on personal injury matters, insurance defense, business disputes, and employment law.


Since he began practicing in 2000, Duffy has litigated cases at both the trial and appellate levels, in both state and federal courts. In his personal injury practice, he has successfully represented clients in disputes regarding the use of public and private property; accidents involving cars, trucks, semi-tractors and trailers, motorcycles, bicycles, and amusement park rides; and animal bites (dog bites and cat bites). In his work for his business clients, Duffy has acted both as general counsel and as litigation counsel, focusing on noncompete agreements, employment discrimination claims, contract and shareholder disputes, trademark infringement claims, trade secret misappropriation, breach of fiduciary duty claims, and insurance coverage litigation. Duffy also has considerable experience handling consumer protection claims, riparian rights issues, and zoning and land use issues. Duffy was honored as a “Wisconsin Rising Star” in Wisconsin Super Lawyers magazine in 2006-2007 and 2009-2014.


Duffy’s father inspired him to become a lawyer. “Before he became a judge, my dad was a highly respected family law attorney. His clients were incredibly grateful for how my dad helped them get through some of the toughest times in their lives. When I realized what a meaningful impact one lawyer could have, I knew I wanted to be a lawyer, too.”


Duffy has litigated hundreds of claims throughout his career. As a seasoned trial lawyer, he relies on his judgment and extensive experience to achieve results. “My clients depend on me to help them resolve difficult issues in their best interests. My first priority is to understand my client’s concerns and make them my own. I love taking cases to trial, but a trial isn’t always the best strategy for accomplishing a client’s objectives. Finding the best way to achieve my client’s desired outcome is always a win, whether the approach involves litigation or not.”


Duffy graduated from University of Notre Dame with a Business Administration (Accounting) degree and received his law degree from University of Wisconsin-Madison. While attending law school, he served as Senior Administrative Editor of the Wisconsin Law Review and published "Child Custody and the Developmentally Disabled Parent," 2000 Wisconsin Law Review 127. He is a distinguished member of the American Bar Association, Rock County Bar Association (past president), James E. Doyle Chapter of the American Inns of Court, and State Bar of Wisconsin.


While Duffy represents clients from across the country, the vast majority of his clients are based in southern Wisconsin and Rock County. “My clients come from different walks of life and have different problems to solve. No matter what the issue may be, it is a privilege for me to represent each one of them and help them reach the right resolution.”


When not practicing law, Duffy spends his time with his wife and two children and enjoys volunteering in the community. He has served full terms on the board of directors of the Humane Society of Southern Wisconsin and the Janesville Performing Arts Center. He is currently serving on the board of directors of the Janesville Youth Baseball & Softball Association (JYBSA) and as vice-chair of the Janesville Generations Fund, a component fund of the Community Foundation of Southern Wisconsin. On most free evenings and weekends from April through August, he can also generally be found volunteering as a baseball coach somewhere for JYBSA.


“Growing up in the Janesville and Rock County area gave me a tremendous sense of community. It’s important to me to try to pay that sense of community forward any way I can. Getting the opportunity to work on JYBSA’s project to expand the Janesville Youth Sports Complex was especially rewarding because I met some of my best lifelong friends through youth baseball as a kid. I know the new facility is a place where Janesville kids will be forming lasting friendships for generations to come.”


Duffy has been admitted to practice in all Wisconsin State Courts, the U.S. District Courts in the Eastern and Western Districts of Wisconsin, the U.S. District Courts in the Central and Northern Districts of Illinois, the State of Texas Eastern District, and multiple state courts on a pro hac vice basis.


Practice areas


  1. Litigation: 40%
  2. Personal Injury: 40%
    16 years
  3. Employment: 20%

Attorney endorsements

No endorsements

Endorsements from fellow lawyers are an important consideration for many when selecting the right attorney. Be the first to endorse your colleague!

Are you an attorney? Endorse this lawyer

Contact info

Brennan Steil Sc

1 E Milwaukee St
Janesville, WI, 53545-3029


WIGood Standing200003/24/2015
We have not found any instances of professional misconduct for this lawyer.
Avvo contributions
Legal answers
Award nameGrantorDate granted
Rising StarWisconsin Super Lawyers2014
Rising StarWisconsin Super Lawyers2013
Rising StarWisconsin Super Lawyers2012
Rising StarWisconsin Super Lawyers2011
Rising StarWisconsin Super Lawyers2010
Rising StarWisconsin Super Lawyers2009
Rising StarWisconsin Super Lawyers2007
Rising StarWisconsin Super Lawyers2006
Work experience
TitleCompany nameDuration
Attorney/ShareholderBrennan Steil S.C.2000 - 2016
Association namePosition nameDuration
James E. Doyle American Inn of CourtBarrister2007 - Present
Rock County Bar AssociationMember2000 - Present
Legal cases
Case nameOutcome
Glendenning’s Limestone & Ready-Mix Co., Inc. v. Reimer, 2006 WI App 161N/A
Williams v. American Transmission Company LLC, 2007 WI App 246N/A
Cottonwood Financial, Ltd. v. Estes, 2012 WI App 12N/A
See all legal cases 
Publication nameTitleDate
Wisconsin Law ReviewChild Custody and the Developmentally Disabled Parent2000
School nameMajorDegreeGraduated
University of Wisconsin Law SchoolN/AN/A2000
Notre Dame Law SchoolAccountingBBA - Bachelor of Business Administration1997