In 1825, Gardiner was appointed District Attorney of Monroe County. From 1829 to 1838, he was Judge of the Eighth Circuit Court of New York, with jurisdiction over the counties of Allegany, Erie, Chautauqua, Monroe, Genesee and Niagara. The Anti-Masonic excitement, growing out of the disappearance of William Morgan, had now commenced, and perhaps the most important case that came before Judge Gardiner, while on the bench of the circuit court, was that against Elihu Mather who was tried for conspiracy in the abduction of Morgan. After the acquittal of the defendant, a motion for a new trial was made in the New York State Supreme Court. The case is to be found in the fourth volume of Wendell's reports, page 220. The head notes, giving the disposition of the various questions raised, occupy four pages. On many of the points it has ever been a leading case. All the rulings of the judge were sustained by the Supreme Court, and these, and other decisions, gave him the reputation of the model circuit judge. He resigned his judicial office in February 1838, and returned to the practice of law at Rochester.
In November 1844, he was electedLieutenant Governor of New York on the Democratic ticket, with Silas Wright for Governor. Many important questions came before the New York State Senate while he presided. It was the period of the anti-rent disturbances, and various preventive and remedial measures were discussed. The enlargement of the canals, and other questions concerning internal improvements, received attention. One of the most important bills provided for the call of a state convention for the formation of a new constitution. As President of the Senate, Lieutenant Governor Gardiner was the presiding officer of the Court for the Correction of Errors, then the state's highest court of appeal, consisting of the president of the Senate, the senators, chancellor, and justices of the New York Supreme Court. Not many cases were carried to this tribunal, litigation usually ceasing with the decision of the Supreme Court or that of the chancellor, so that most of them were important in principle or amount. Those decided during his presidency can be found in Denio's reports. Gardiner was reelected Lieutenant Governor in 1846, defeating Hamilton Fish, the Whig candidate, by a majority of 13,000 votes, although the Whig's candidate for governor John Young was elected by a majority of more than 11,000 over the incumbent Governor Wright - then, the governor and the lieutenant governor, although running mates, were elected on separate ballots. Gardiner had been nominated on a cross-endorsed ticket with Young by the Anti-Renters whose votes decided this election. Gardiner was among the first judges elected on June 7, 1847, to the new New York Court of Appeals. On June 22, he drew the longest term, and took office on July 5, according to the new State Constitution adopted in 1846. To fill the vacancy in the office of lieutenant governor, a special election was held at the annual State elections, and Fish was elected for the remainder of Gardiner's unexpired term. Gardiner became Chief Judge in 1854, and held the office until the end of 1855 when his term expired.
His opinions
Judge Gardiner's opinions are reported in Denio's, Comstock's, Selden's and the first three volumes of Reman's reports. Among them are the cases of:
Miller v. Gable, on charitable uses, holding that chancery, under its general jurisdiction over trusts, will interfere, on behalf of members of a religious corporation to which a fund has been granted, to prevent it from diverting the fund to promote the teaching of doctrines essentially variant from those designated, but not as to lesser shades of doctrine.
Mayor of New York v. Baily, holding that an action on the case for malfeasance will be against the corporation; if the city be empowered by statute to construct works, the state reserving the power to appoint commissioners to superintend the construction, the acceptance of the act by the city renders it liable for injuries arising for want of skill, or neglect, in building the works.
Danks v. Quackenbush, in which he dissented, with three others of the judges, constituting one-half of the court, from the opinion of the four others, that the act of 1842, extending the exemption of personal property from the sale under execution, is unconstitutional and void as to debts contracted before its passage.
Leggett v. Perkins, holding that a trust to receive and pay over the rents and profits of land was valid, under the statute authorising a trustee to receive the same and apply them to the use of any person.
People v. Schuyler, reversing the decree of the Supreme court, and holding that if the sheriff after the jury have found for a claimant, refuses to deliver the property, the surety on his official bond is liable, though the creditor does not indemnify him, and, where he requires and receives indemnity before selling and judgment is afterwards recovered against him for the erroneous seizure, his sureties, on payment of the judgment, are entitled to be subrogated to the indemnity.
Chautauqua Co. Bank v. White, holding that an assignment by the debtor to the receiver of all his real property leaves no residuary interest in the debtor, and reversing the decree of the Supreme court, and affirming that of the vice-chancellor.
Nicholson v. Leavitt, reversing with the concurrence of all the judges, the judgment of the Superior court of the city of New York, and holding that an assignment by insolvent debtors of their property to trustees for the benefit of their creditors, with an authorisation to the trustees to sell the assigned property upon credit, is fraudulent and void as against the creditors of the assignees.
Talmage v. Pell, on the powers of banking associations, reversing the judgment of the Supreme court.
Kundolf v. Thalheimer, on the powers of county courts, reversing the judgment of the Supreme court.
Later life
After his retirement from the Court of Appeals he continued to lend his aid in the administration of justice as a referee. For twenty years, he arbitrated many important causes. He died in Rochester and was buried at Mt. Hope Cemetery in Rochester.
Family
In 1831 he married Mary Selkrigg, of Scotch descent. Their children were Charles A. Gardiner and Celeste M. Gardiner. His oldest brother, William Gardiner,, resided several years in Lowell, Massachusetts, then removed to Texas, where he died on his plantation near San Antonio. Another brother, Charles was a merchant in New Orleans. His sister Rebecca, married Oren Stone, a merchant, and the partner of Governor Seymour's father, and lived at Watertown, New York. Another sister, Dorothy, married Thomas A. Gould, a lawyer of Pittsfield, Massachusetts, where she died in 1857. The youngest sister, Louisa, born about 1800, married Elijah Rhoades, of Manlius, a merchant and New York State Senator.