Gerard was born in 1794 in New York City, of Scotch and French descent. His father, William Gerard, born in Banff in the Highlands of Scotland, was a member of a French family which had fled thither to escape religious persecution. He emigrated about 1780 to New York City, where he married Christina Glass and became a prosperous merchant.
Gerard obtained his early education from private tutors. Entering Columbia College while yet a boy he graduated in 1811, being third in his class and distinguishing himself in mathematics and the classics.
On the outbreak of the War of 1812, Gerard enlisted and served in one of the volunteer companies raised for the purpose of defending New York City. On the conclusion of the war he entered the office of George Griffin, one of the leading New York lawyers, and was admitted to the bar in 1816. He had read widely, and was instrumental in forming a debating society called the Forum, in whose discussions he, with Fessenden, Hoffman, and other brilliant juniors constantly participated. His first retainer was on behalf of a boy fourteen years old who was indicted for the theft of a canary, and the circumstances of the case - it being the accused's first offense - made so strong an impression upon him that he determined to take steps to assist in the reformation of junior offenders. He joined the Society for the Prevention of Pauperism, and was a prime mover in the appointment of a special committee which investigated the subject of juvenile delinquency. He strongly advocated the creation of an asylum for youthful criminals where they would be safe from contamination by hardened convicts, and procured the incorporation, on March 29, 1824, of the Society for the Reformation of Juvenile Delinquents, whose House of Refuge, built shortly, was the first institution of its kind in the country. As a member of the board of managers, Gerard contributed powerfully to its successful operation. Though he was now enjoying an extensive practice at the bar, he continued to devote much of his time and means to social reform. In 1854, having always been a consistent opponent of slavery, he took a leading part in the agitation against the passage of the Kansas-Nebraska Bill. His greatest services in his later years were rendered in the cause of popular education. For twenty years, first as a school trustee and later as inspector of the fifth school district, he was indefatigable in raising the standard of public educational training. Though on more than one occasion offered the position of commissioner of the Board of Education, he uniformly declined that and all other public office, maintaining that he could do more effective work as inspector than in any other capacity. After his retirement from legal practice in 1869 he devoted all his time to the improvement of educational methods. As a lawyer, he had an uneventful career, distinguished only by a steady advancement to the headship of the New York bar. Industry and perseverance were his chief characteristics, but he was an advocate by instinct and became the leading jury lawyer of his time.
Gerard devoted much of his time and means to social reform, identifying himself with all movements having for their object the amelioration of distress, the advancement of the best interests of the city, and efficient administration. He induced great reforms in the police system and was the first to advocate the wearing of uniforms by policemen.
Gerard married on October 3, 1820, Elizabeth, daughter of Increase Sumner, chief justice of the supreme judicial court and governor of Massachusetts.
