Joseph McMahon | Griffin Williams McMahon & Walsh Geneva IL Lawyer

Joseph McMahon


Joseph H. McMahon is a highly respected and accomplished lawyer who focuses his practice on the areas of business counseling, high-stakes litigation, crisis management, and white-collar crime. Throughout his career, Joe has built a reputation as an elite trial lawyer and a careful and discrete problem solver and advisor to key executives in government, manufacturing, media and private equity. Joe has extensive experience, as an advisor and general counsel to his corporate clients, in complex disputes on both sides of the table, and in “bet-the company” litigation in the areas of healthcare fraud, catastrophic injury, civil rights, as well as high stakes government and regulatory investigations and enforcement.

During his tenure as State’s Attorney for Kane County, Illinois, Joe represented the fifth largest county in Illinois in all matters and led one of the largest prosecutor’s offices in Illinois. As State’s Attorney, Joe oversaw successful investigations and prosecutions in the areas of financial crimes, public corruption, violent crimes, large-scale drug trafficking, homicide, and civil matters in the areas of labor and employment, civil rights, environmental matters, zoning and development and litigation in both state and federal courts. Joe’s diverse background, comprehensive trial experience, coupled with his management abilities, position him as a valuable advocate and trusted advisor to his individual, municipal, and business clients.

In 2016, he was appointed the Special Prosecutor in the investigation and prosecution of former Chicago police officer, Jason Van Dyke for the murder of Laquan McDonald, a case commanding national attention for several years. In that case he served as lead trial attorney in the years’ long investigation and jury trial covered by local, national, and international media groups. WTTW Chicago’s public broadcast television station described the conviction as a “landmark monthlong trial” and the conviction marked the first successful prosecution of a Chicago police officer for murder in approximately 50 years.

Joe’s experience in courtrooms, boardrooms and conducting investigations on sensitive matters makes him especially qualified to conduct internal investigations and guide clients in managing through their most critical crises so executives can get back to running their business.

Joe was the Illinois state director for the National District Attorney’s Association and served on its executive committee where he developed a non-partisan coalition that includes members of Congress, the United States Department of Justice, members of the Illinois General Assembly and state and federal prosecutors across the country. As state’s attorney, he was selected by his peers to serve on the board of directors of the Illinois State’s Attorney’s Appellate Prosecutors and he was chair of the Illinois State’s Attorney’s best practices committee where he led efforts to identify and implement model programs in the areas of diversion, eye-witness identification, prosecutor training and trial practice for prosecutors’ offices across Illinois. As State’s Attorney he served over 500,000 constituents in Northern Illinois, and more broadly served in roles with national reach. He worked closely with the United States Department of Justice (DOJ) in the Northern and Central District of Illinois, the Federal Bureau of Investigation in Chicago and Washington D.C. and the federal joint terrorism task force.

He has extensive private practice experience defending class actions stemming from the Telephone Consumer Protection Act (TCPA), qui-tam claims brought against individual medical professionals, practice groups and health systems under the False Claims Act in healthcare billing, and allegations of consumer and mortgage fraud including those brought by state and federal regulatory agencies. He obtained a verdict in favor of his client, an automobile leasing company against claims of consumer fraud brought by a former member of the Rockettes and served as outside general counsel to a minor league professional sports team. He has served as lead negotiator for his clients and secured non-prosecution agreements, favorable settlements and dismissals for his clients facing regulatory enforcement with draconian statutory damages, exclusionary and debarment provisions.

Professional Background

Mr. McMahon is a co-founder of Griffin Williams McMahon & Walsh, LLP. Before returning to private practice, he was the elected state’s attorney in Kane County, Illinois and previously in private practice as co-founder of McMahon Williams and as a partner in one of the largest national law firms in the United States. He also served as a deputy prosecutor in the Illinois Attorney General’s Office where he led the investigation and prosecution of public corruption and healthcare fraud in government run and administered healthcare programs.

Mr. McMahon is a member of the American Bar Association, the Illinois State Bar Association and is a past chair of both the corporate law departments section council and the corrections and sentencing committee. For more than a decade he served on the judicial evaluation committee outside of Cook County for the Illinois State Bar Association.

Mr. McMahon has been an instructor for the Northeast Multi-Regional Training Institute (NEMRT) for state and federal law enforcement officers and was the coordinator for the Illinois Attorney General’s Trial Advocacy Program from 2000-2001.

Presentations, Publications & Awards

Mr. McMahon has spoken extensively on issues related to anti-crime initiatives, fraud, white-collar crime, social justice, employment matters and internal corporate investigations. He was an instructor for the National District Attorney’s Association in the area of prosecutor ethics and has been an instructor and guest lecturer at Loyola University, Northern Illinois University College of Law, Lake Forest College, community colleges throughout Northern Illinois and the Illinois State Bar Association.

Some of his presentations include:
  • “State and Federal Law Enforcement Collaboration”
    United States Department of Justice, Federal Bureau of Investigation, Joint Terrorism Task Force, Chicago, Illinois October 26, 2020
  • “Innovations in Prosecutions, Officer Involved Shootings,”
    National District Attorneys Association, Quebec City, Quebec, Canada, July 24, 2019
  • “Identifying and Combatting Sex Trafficking,”
    Chicago Healthcare Risk Management Society, Chicago, Illinois April 26, 2019
  • “Prosecuting Officer Involved Shootings,”
    Mississippi Prosecutors Association, Oxford, Mississippi, April 23, 2019
  • “Litigation Challenges in Officer Involved Shootings”,
    Prosecutors Center for Excellence, Washington D.C. January 30, 2019
  • “Conflicts and Ethics in Large Prosecutors’ Offices,”
    National District Attorneys Association, Denver, Colorado, July 23, 2014

Mr. McMahon is a co-author of “The New Perils of White-Collar Crime,” published in 2006 by Aspatore Books. His chapter, “Getting the Client Back to Business,” was also published as part of an Executive Business Report in Business Wire, in the July 2006 issue.

In addition to Mr. McMahon’s professional presentations he has given hundreds of interviews on television, radio and in print media on high-profile matters, during times of civil unrest and following court proceedings on matters of heightened public interest on news programs such as ABC7 Eyewitness News, NBC5 Chicago and NBC13 Rockford, CBS2 Chicago, WGN, Telemundo and Fox News Chicago, WTTW | Chicago’s PBS station and Embedded, a syndicated podcast of National Public Radio (NPR) and on radio programs in the Chicago media market on WGN, WVON and WBBM and quoted extensively in print media in the Chicago Tribune, Chicago Sun-Times and the Suburban Daily Herald.

Community Involvement & Awards

Joe has served on the not-for-profit board of directors, including as chair, of Fox Valley Hospice (now Hands of Hope) the largest volunteer hospice organization in the United States and the City of Elgin’s Parks and Recreation advisory board. He has been formally recognized for his commitment and support of civil rights, mental health services and public safety by numerous organizations including the City of Aurora, the Alliance Against Intoxicated Motorists, Family Services Association of Greater Elgin Area, the Community Crisis Center, the Quad County Urban League, the Illinois States Attorneys Association and Fight Crime, Invest in Kids.
  • The University of Notre Dame,
    Master of Business Administration,
    2006 Magna Cum Laude
  • The John Marshall Law School,
    Juris Doctor, 1992
  • The University of Iowa, Bachelor of Business Administration, Finance, 1988
Bar Admissions
  • State of Illinois
  • United States Supreme Court
  • United States District Court, General and Trial Bar for the Northern District of Illinois
Practice Areas
  • Business Law
  • Civil & Commercial Litigation
  • Crisis Management
  • Healthcare Litigation
  • Independent & Internal Investigations
  • Municipal & Local Government
  • Government Investigations and Regulatory Enforcement*
  • White-Collar and Criminal Defense

Representative Cases

People of the State of Illinois vs. Jason Van Dyke, Circuit Court of Cook County, Illinois. Special prosecutor appointed in the criminal case against former Chicago police officer resulting in jury verdict of guilty for second degree murder and 16 counts of aggravated battery for the 2014 killing of Laquan McDonald.

United States ex rel. Fields vs. Sherman Health Systems, et al, United States District Court, Northern District of Illinois. Defense of Health System against alleged violations of the False Claims Act for violations of Medicare and Medicaid regulations, the Anti-kickback act, and federal Stark laws. The case was originally filed under seal and submitted to the United States Department of Justice who declined to intervene and ultimately dismissed with prejudice based on defense motions.

Juliette Stege vs. Riverfront Chrysler Plymouth, Inc. and Gold Key Leasing, Inc., 16th Judicial Circuit, Kane County, Illinois. Defense of leasing company against statutory and common law fraud claims, including claim for punitive damages. Verdict in favor of leasing company resulting in no liability.

Wendy Gossett vs. Sherman Health Systems and Sherman Hospital, 16th Judicial Circuit, Kane County, Illinois. Defense of hospital and health systems in medical malpractice claim resulting from a medical sponge left inside plaintiff’s abdomen post-surgery. Jury verdict award to plaintiff was $6.5 million less than plaintiff claimed in damages.

Multi-District 300 Lions Clubs of Taiwan vs. International Association of Lions Clubs, 18th Judicial Circuit, DuPage County, Illinois and Boston, Massachusetts. Defense of declaratory judgment action and subsequent arbitration hearing before panel of 9 international arbitrators seeking right to exclusive use of Lions Clubs™ and development of member clubs in Taiwan and mainland China. Obtained dismissal in state court, (affirmed on appeal) and entry of award of arbitrators in favor of the association.

People of the State of Illinois vs. Maurice King, 16th Judicial Circuit, Kane County Illinois. Prosecution of double homicide of mother and her four-year-old child resulting in life sentence.