Skilled Trial & Appellate Attorney

Thomas G. Cannon is Of Counsel to the law firm of O’Neil, Cannon, Hollman, DeJong & Laing S.C.


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.

Community Service

  • 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.”


  • 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


  • 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).