Jack Tanner's father, Ernie Tanner, was an exceptional man who had a strong influence on his son's life. In 1918, Ernie Tanner, who was one of the first African-American Union advocates in the United States, fought for the inclusion of blacks into the longshoremen's union. Judge Tanner was himself a member of the longshoremen's union for fourteen years in Tacoma, Washington, and continued to work on the waterfront when he graduated from the University of Washington Law School in 1955.

Jack Tanner never forgot his father's efforts to better the world he lived in. Ultimately, Judge Tanner's decision to become a lawyer was not only influenced by this belief in advocacy, but also based upon his own experiences in the "Jim Crow" United States Army during World War II. Tanner says, "that experience was the factor in my decision to become a lawyer."

Judge Tanner has had a distinguished judicial career and has written a number of opinions of significance, particularly in the area of civil rights and civil liberties. For example, in 1980, Judge Tanner ruled that the condition of Washington State's Walla Walla penitentiary violated "society's minimum standards of decency, inflict[ed] purposeless pain and suffering", and that forcing individuals to serve time at Walla Walla constitut[ed] cruel and unusual punishment within the meaning of the Eighth Amendment." Also, in his 1983 landmark decision which came to be known as the "Comparable Worth" case, Judge Tanner found that Washington state's policy of paying lower salaries for thousands of jobs held predominantly by women than by comparable jobs held by men, was an example of "pervasive and intensive" wage discrimination by the state. In 1985, he found that a high school in Washington state could not suspend a student for giving a speech school officials found obscene. 

Judge Tanner has also been active in the community. He is a past Chair of the NAACP; he served on the Association's National Board of Directors when Justice Thurgood Marshall was its General Counsel. Tanner is also a recipient of numerous honors and awards, including the William H. Hastie Award for outstanding legal scholarship: the Loren Miller Bar Association Award for distinguished service, progressive judicial vision, and inspiration; and the Thurgood Marshall Achievement Award. 

In recognizing Judge Tanner's outstanding and dedicated service for the betterment of civil and human rights for all, Booth Gardner, Governor of the State of Washington, commented:

In his noteworthy career, Judge Tanner has heard many of the most complicated legal cases in Washington State's history. His admirable decision on the landmark Comparable Worth Case has contributed a very positive influence on justice and equality, in our state and in the nation. I applaud Judge Jack Tanner's dedication to public service.