Born a son of farmers in Newberry, Massachusetts, Moody graduated from Phillips Academy in 1872 and from Harvard in 1876, where he was a classmate and friend of future President Theodore Roosevelt. After 4 months attending Harvard Law, he departed and instead took the then-common but now-unusual step of reading law under Richard Henry Dana to pass the bar.

Early in his legal career, Moody first was elected city solicitor of Haverhill in 1888. After appointment as the US Attorney for Eastern Massachusetts in 1890, he gained widespread notoriety in 1893 as the junior prosecutor in the Lizzie Borden murder case. While his efforts were unsuccessful he was generally acknowledged as the most competent and effective of the attorneys on either side. He was elected to the U.S. House of Representatives from Massachusetts, and served from 1895 until 1902 where he served on the powerful Appropriations Committee. During President Theodore Roosevelt's administration, Moody served as the Secretary of Navy (1902-1904) and as Attorney General (1904-1906). As Attorney General, Moody actively followed Roosevelt's trust-busting policies, negotiating with 'good' trusts like U.S. Steel but prosecuting 'bad' ones like Standard Oil. After failing to convince William Howard Taft to take the seat, on December 12th, 1906, Roosevelt nominated Moody as an Associate Justice of the U.S. Supreme Court and Moody was confirmed December 17th, 1906.

Moody's service on the Court was brief but not uneventful, writing 67 opinions and 5 dissents. His most noted opinion was in the minority in Employers Liability Cases (1908), where he held that Congress' power to regulate interstate commerce included the ability to legislate management's relationship with employees. While he generally supported enhanced federal powers, opinions as Twining v. New Jersey (1908) where he held the right to self-incrimination did not apply to cases presented in state courts made him hard to pidgeonhole.

By 1908, Moody suffered severe rheumatism. This affected Moody to such an extent that his last sitting on the bench was May 7, 1909, when he left for a brief rest and never returned. With the age- and health-enfeebled Supreme Court of 1909 crippled (President William Howard Taft was to make a record setting 5 appointments due to death and resignations over a course of a year in 1910-1911), Taft urged Moody, then the youngest justice at 55, to step down. After Taft successfully lobbied Congress on for a Special Act to grant Moody retirement benefits not normally granted unless justices reached age 70 or 10 years of service (enacted June 23, 1910), Moody retired from the Court on November 20, 1910. He died in Haverhill, Massachusetts, July 2, 1917.

USS Moody (DD-277) was named for him, as is one of the major streets in Waltham, Massachusetts.

This article includes text from the public domain Dictionary of American Naval Fighting Ships.

Preceded by: John D. Long United States Secretary of the Navy 1902-1904 Succeeded by: Paul Morton Preceded by: Philander C. Knox Attorney General of the United States 1904-1906 Succeeded by: Charles Joseph Bonaparte Preceded by: Henry Billings Brown Associate Justice of the Supreme Court of the United States December 17, 1906-November 20, 1910 Succeeded by: Joseph Rucker Lamar