On May 1, 1871, he went to Salt Lake City in connection with mining litigation, and while there was retained by Brigham Young as an attorney and general counsel to the Church.
He was in charge of all the criminal and civil litigation in which Brigham Young and other Church leaders were involved.

On October 2, 1871, Brigham Young, Daniel H. Wells and others were served with an arrest warrant by U. S. Marshal at Young's residence in Salt Lake City.
He was charged with lewd and lascivious cohabitation with his plural wives but allowed to remain in his home guarded by a marshal.
The next day Apostle George Q. Cannon was also arrested on similar charges.
On October 9, 1871, Brigham Young appeared before Chief Justice Thomas McKean in the case of People versus Brigham Young, Sr.. Fitch represented the church leaders and arranged for Young's bail.
Fitch moved to quash the indictment.

On October 12, Judge McKean issued his decision on Fitch's motion to quash the indictment in which he positioned the case as a trial of the entire church.

But let the counsel on both sides, and the court also, keep constantly in mind the uncommon character of this case.
The supreme court of California has well said: " Courts are bound to take notice of the political and social condition of the country which they judicially rule."
It is therefore proper to say, that while the case at bar is called, "The People versus Brigham Young" its other and real title is, "Federal Authority versus Polygamic Theocracy."..
A system is on trial in the person of Brigham Young.

McKean charged the defense with "proving that the polygamous practices charged in the indictment are not crimes."
On October 16, Young pleaded innocent.
The attorneys asked for time to prepare for the case and based on McKean's ruling, Fitch inferred that the trial would proceed in March.
Young departed for St. George, Utah and Fitch left for New York.
Shortly after their departure, McKean set the trial date for November 20.
Assistant defense attorney Hempstead protested, and the prosecutor demanded forfeiture of Young's bail.
The Associated Press ran a story that Brigham Young had fled from justice.

William "Wild Bill" Hickman, who had been arrested and jailed for murdering government arms dealer Richard Yates during the Utah War, implicated Brigham Young and others in Yates' murder.
Hickman was excommunicated from the church as a result, although he was never convicted, nor was Young ever indicted based on his testimony.
On April 15, 1872, the U. S. Supreme Court ruled in "Clinton et al vs. Englebrecht et al" that McKean's indictments were invalid, and Young and others were released from further prosecution.

He was elected a member of the 1872 Utah Constitutional Convention On the second day of the convention, he harshly criticized federal Judge McKean, who had been appointed by President Grant in 1870 as Chief Justice of Utah Territorial Supreme Court.
McKean had removed virtually all locally elected officials from their roles and supplanted their authority with federal officials he appointed.
McKean believed that he had a divinely appointed  mission in Utah, "to the carrying out of which he was evidently prepared to subordinate all other considerations."
He said this included "whenever and wherever I may find the local or federal laws obstructing or interfering therewith, by God's blessing I shall trample them under my feet."
Fitch described him as "A sort of missionary exercising judicial functions," "a very determined man," "of considerable personal courage," "but not fit to be a judge."

During February and March Fitch spoke eloquently about the political necessity of forgoing polygamy from the Utah state constitution.

I am not here to attack polygamy from a theological, moral, or physical, but from a political standpoint.
Certainly I do not propose to question the pure motives or the honesty of those who believe in and practice it.
I am inclined to agree with Montesquieu and Buckle, that it is an affair of latitude and climate and race, and on these grounds alone its existence among a S
On May 1, 1871, he went to Salt Lake City in connection with mining litigation, and while there was retained by Brigham Young as an attorney and general counsel to the Church. He was in charge of all the criminal and civil litigation in which Brigham Young and other Church leaders were involved.
On October 2, 1871, Brigham Young, Daniel H. Wells and others were served with an arrest warrant by U. S. Marshal at Young's residence in Salt Lake City. He was charged with lewd and lascivious cohabitation with his plural wives but allowed to remain in his home guarded by a marshal. The next day Apostle George Q. Cannon was also arrested on similar charges. On October 9, 1871, Brigham Young appeared before Chief Justice Thomas McKean in the case of People versus Brigham Young, Sr.. Fitch represented the church leaders and arranged for Young's bail. Fitch moved to quash the indictment.
On October 12, Judge McKean issued his decision on Fitch's motion to quash the indictment in which he positioned the case as a trial of the entire church.
But let the counsel on both sides, and the court also, keep constantly in mind the uncommon character of this case. The supreme court of California has well said: " Courts are bound to take notice of the political and social condition of the country which they judicially rule." It is therefore proper to say, that while the case at bar is called, "The People versus Brigham Young" its other and real title is, "Federal Authority versus Polygamic Theocracy."..A system is on trial in the person of Brigham Young.
McKean charged the defense with "proving that the polygamous practices charged in the indictment are not crimes." On October 16, Young pleaded innocent. The attorneys asked for time to prepare for the case and based on McKean's ruling, Fitch inferred that the trial would proceed in March. Young departed for St. George, Utah and Fitch left for New York. Shortly after their departure, McKean set the trial date for November 20. Assistant defense attorney Hempstead protested, and the prosecutor demanded forfeiture of Young's bail. The Associated Press ran a story that Brigham Young had fled from justice.
William "Wild Bill" Hickman, who had been arrested and jailed for murdering government arms dealer Richard Yates during the Utah War, implicated Brigham Young and others in Yates' murder. Hickman was excommunicated from the church as a result, although he was never convicted, nor was Young ever indicted based on his testimony. On April 15, 1872, the U. S. Supreme Court ruled in "Clinton et al vs. Englebrecht et al" that McKean's indictments were invalid, and Young and others were released from further prosecution.
He was elected a member of the 1872 Utah Constitutional Convention On the second day of the convention, he harshly criticized federal Judge McKean, who had been appointed by President Grant in 1870 as Chief Justice of Utah Territorial Supreme Court. McKean had removed virtually all locally elected officials from their roles and supplanted their authority with federal officials he appointed. McKean believed that he had a divinely appointed  mission in Utah, "to the carrying out of which he was evidently prepared to subordinate all other considerations." He said this included "whenever and wherever I may find the local or federal laws obstructing or interfering therewith, by God's blessing I shall trample them under my feet." Fitch described him as "A sort of missionary exercising judicial functions," "a very determined man," "of considerable personal courage," "but not fit to be a judge."
During February and March Fitch spoke eloquently about the political necessity of forgoing polygamy from the Utah state constitution.
I am not here to attack polygamy from a theological, moral, or physical, but from a political standpoint. Certainly I do not propose to question the pure motives or the honesty of those who believe in and practice it. I am inclined to agree with Montesquieu and Buckle, that it is an affair of latitude and climate and race, and on these grounds alone its existence among a S
Thomas Fitch (politician)