Attorney Gardner graduated from the University of New Hampshire in 1969, and received his law degree from Boston University in 1972 where he also served as an editor of the Boston University Law Review. He is board certified as a civil trial specialist by the National Board of Trial Advocacy, is a member of the New Hampshire and American Bar Associations, the New Hampshire Trial Lawyers Association, the American Association for Justice (formerly The Association of Trial Lawyers of America), is a Senior Counsel member of the College of Master Advocates and Barristers and is an Associate of the American Board of Trial Advocates.

He has earned recognition as an Advocate of the National College of Advocacy of the American Association for Justice and has served as a past national officer of the American Association for Justice . He is admitted to practice before the United States Supreme Court, the United States Court of Appeals for the Second Circuit, the United States Court of Federal Claims, and the highest state courts of New Hampshire, Vermont and Massachusetts as well as the United States Federal District Courts of New Hampshire, Massachusetts, and Vermont.

He is a Fellow of the New Hampshire Bar Foundation, a past member of the New Hampshire Supreme Court Committee on Professional Conduct and a former law clerk to the New Hampshire Supreme Court. He has in the past served on a variety of New Hampshire Bar Association, New Hampshire Trial Lawyers and American Association for Justice committees and has served as a panelist and lecturer on continuing legal education programs. Attorney Gardner has achieved the highest possible peer review rating from LAWDRAGON and is listed in Who's Who in America and Who's Who in American Law.

He is a past officer and director of the Monadnock United Way, the Keene Family YMCA and the Greater Keene Chamber of Commerce and has served as chairman of the Cheshire County Crimestoppers, Inc.