De Lancey Nicoll was born on June 24, 1854 at Shelter Island, New York, United States. He belonged to a family prominent in New York for nearly three centuries. He was a son of Solomon Townsend Nicoll, a successful East India merchant, and of Charlotte Ann (Nicoll) Nicoll; and through both his parents was descended from Matthias Nicolls, a London barrister who came to New York in 1664 as secretary of the Duke of York's commission.
After attending various private schools, De Lancey Nicoll completed his college preparatory work at St. Paul's School, Concord, New Hampshire, he was graduated from the College of New Jersey (Princeton) in 1874 and from the Columbia Law School two years later.
After his admission to the bar in 1876 and a short apprenticeship in the offices of Clarkson N. Potter and of Julien T. Davies, he began practising in partnership with Walter D. Edmonds.
In 1885, while still comparatively unknown at the bar, he was appointed assistant district attorney of New York County. A series of brilliant prosecutions brought him immediate recognition as an outstanding trial lawyer. Among others he convicted Frederick Ward, the partner of General Grant, of brokerage frauds; and four of the notorious "boodle" aldermen, or "combine of thirteen" (the rest having fled to Canada), of having accepted bribes to grant a street rail, way franchise on Broadway.
In 1887 he was the unsuccessful candidate of independent Democrats and Republicans for district attorney; but three years later he was elected on the Tammany ticket. The duties of the office were administrative, and Nicoll was chiefly engaged in directing and advising a group of able assistants whom he had appointed. At the close of his term he refused a renomination and resumed his practice. Among his clients were labor organizations, the New York World, the Interborough Rapid Transit Company, and the American Tobacco Company. Three cases which he argued before the Supreme Court of the United States were of unusual interest. In the Panama Libel case which concerned the publication by the World of sensational exposures of scandals in the acquisition of the Canal Zone, Nicoll was pitted against the whole executive department of the government from the President down. Basing his defense chiefly on narrow legal grounds, but with some attention to the constitutional aspects of the case, he won a significant victory for a free press.
In defending the American Tobacco Company in anti-trust proceedings, he argued for a reasonable interpretation of the Sherman Act and perhaps suggested the "rule of reason" which the Supreme Court announced in another case and considerably extended in this case. After the decision, which went against his client, he successfully applied the "rule of reason" in the dismemberment of the company. Besides utilizing the resources of precedent and legal principles, Nicoll showed great originality in the preparation and presentation of cases.
In politics Nicoll was always a Democrat except in 1896, when he voted for McKinley.
As a member of the state constitutional conventions of 1894 and 1915 he supported the short ballot and other genuine reforms but fought against specious proposals. He hated demagogues and professional altruists.
Nicoll liked difficult cases and was at his best before judges who were unsympathetic toward his clients.
In private life he was a brilliant wit and a rare friend.
Nicoll married Maud Churchill of Savannah, Georgia, on December 11, 1890, and had a son and a daughter. Only the son survived him.
