Thomas G. Cannon

Tel | 414.276.5000




  • University of Wisconsin Law School
  • Marquette University (B.A.)

Thomas G. Cannon

Skilled Trial & Appellate Attorney

Tom currently serves as Of Counsel to the law firm of O’Neil, Cannon, Hollman, DeJong & Laing S.C. He is an experienced trial and appellate lawyer with an extensive background in complex litigation. He has also served as an expert witness and consultant to other lawyers in the fields of legal ethics and constitutional law.

Experience/Representative Client Work

Cannon has been recognized as one of Wisconsin’s most prominent trial and appellate attorneys for more than four decades. Career highlights include:

  • A Wisconsin Law Journal article portraying Cannon as a modest “superhero” for his legal work on behalf of Milwaukee’s poor and disabled. (August 30, 2006)
  • A Milwaukee Journal account of a highly-publicized jury trial describing Cannon as “a bulldog attorney” for his cross-examination of a powerful corporate executive, noting that, “as Cannon sharply interrogated [the witness], the normally articulate business wizard was reduced to stammering.” (December 22, 1994)
  • A Milwaukee Magazine feature on another of Cannon’s celebrated trials praised his “skilled lawyer’s dispassionate” handling of “the biggest Wisconsin civil case of the decade.” (October 1993). The five-and-a-half-month trial involved a successful struggle for control of the world’s largest religious foundation.
  • A Milwaukee Sentinel profile likened Cannon’s courtroom presence to “a low-key lightning bolt.” (April 16, 1976). The article highlighted Cannon’s receipt – just five years out of law school – of his first Lawyer of the Year award.
  • In 1998, the Wisconsin Supreme Court appointed Cannon to represent a Circuit Court judge in a case concerning the legal authority of judges to impose sanctions on attorneys. Anderson v. Circuit Court, 219 Wis.2d 1, 578 N.W.2d 633. (1998)
  • In 1997, a panel of senior judges selected Cannon to represent the state’s 250 Circuit Court judges in a Wisconsin Supreme Court case defining the constitutional power of trial judges. Barland v. Eau Claire County, 216 Wis.2d 559, 575 N.W.2d 691. (1998)
  • The Chief Judge of Milwaukee County appointed Cannon to represent all Milwaukee judges in complex litigation involving under-funding of the judicial branch of government. “Lawyer says courts can order funds” in Milwaukee Sentinel. (February 4, 1991)
  • Cannon served as a professor of constitutional law and legal ethics at Marquette University Law School, 1981-1985.
  • Cannon has held the Martindale-Hubbell Law Directory’s highest peer-reviewed rating for legal ability and ethical behavior since 1980.


  • Wisconsin Supreme Court Chief Justice Nathan Heffernan described a brief written by Cannon as “the best brief I’ve ever read.” Remarks to Milwaukee Bar Association Annual Dinner, 1991.
  • Chief Judge Patrick Sheedy characterized the same Cannon brief as “an absolutely superb job.” (Milwaukee Sentinel, February 4, 1991)
  • Lifetime Achievement Award by the Wisconsin Equal Justice Fund (2011)
  • Leader in the Law Award by the Wisconsin Law Journal (2010)
  • Martindale-Hubbell® Peer Review Rating™–AV Preeminent, reflecting an attorney who has reached the height of professional excellence and is recognized for the highest levels of skill and integrity
  • Wisconsin Super Lawyer (2007)
  • Outstanding Lawyers of America (2003)
  • Leading Wisconsin Lawyer (2000)
  • Lawyer of the Year by the Milwaukee Bar Association (1991)
  • One of Milwaukee Magazine’s Top Lawyers (1990)
  • Milwaukee Magazine named Cannon one of the city’s “most interesting people” (January 1989).


  • Author of Equal Justice: A History of the Legal Aid Society of Milwaukee (Marquette University Press, 2010), 440 pages
  • Quoted as a legal authority in such publications as the New York Times, Wall Street Journal, Chicago Tribune, Washington Post, and National Law Journal
  • Board of Editors, American Journal of Comparative Law (1982-1985)
  • Contributing Editor, Preview of U.S. Supreme Court Cases (American Bar Association, 1983-1985)
  • Presenter at numerous Judicial Education and Legal Education seminars

Community Involvement

  • In 1999, the Milwaukee County Sheriff cited Cannon “for heroic action” in saving the lives of ten passengers when he grabbed the wheel of an out-of-control bus as it careened off the freeway and crashed through a traffic sign at 60 m.p.h. One passenger told reporters, “That was a pretty brave thing to do.” Local news anchor Kathy Mykleby said of Cannon’s actions: “Wow! That was a phenomenal thing that he did. He is a hero.” (WISN-TV, April 8, 1999)
  • President, Wisconsin Coalition Against the Death Penalty (2004-present)
  • President, Hunger Task Force of Milwaukee (2004-2005)
  • President, Irish Genealogical Society of Wisconsin (2000-2002)
  • President, Legal Aid Society of Milwaukee (1995-2003)
  • President, Milwaukee Montessori School (1982-1983)
  • Pro Bono Publico Award from the Posner Foundation for his legal work with the homeless (1991)
  • Member, City of Milwaukee Ethics Board (1979-1980)
  • Cannon served as a U.S. Marine in Vietnam in 1968-1969. His decorations include the Combat Action Ribbon for “satisfactory performance under enemy fire” and the Vietnamese Cross of Gallantry Ribbon for “valorous combat achievement.”