Lacy was born on the family plantation, Ellsworth, in New Kent County, Virginia, the son of lawyer and future delegate Richmond Terrell Lacy and his wife the former Ellen Green Lane. The firstborn son received his early education from his mother, after which he attended Pike Powers Academy in Staunton and Brown and Tebbs Academy in Albemarle County. He had an elder sister Sally E. Lacy, as well as a younger sister Ellen G. Lacy and two younger brothers Richmond Terrell Lacy and Thomas Hugo Lacy. Completing his formal education at the University of Virginia, Lacy then read law under his father's guidance. On November 14, 1878, he married Sarah Rebecca Osborne 1858 - 1936), daughter of a Presbyterian minister. They had four children who survived their father.
After the war, Lacy refreshed his studies, was admitted to the Virginia bar in 1866 and practiced law together with his father. In 1870, he was appointed to the county court of Charles City and New Kent Counties and remained there for three years until the General Assembly reorganized the judiciary. Voters then elected Lacy to the Virginia House of Delegates to represent Charles and New Kent counties. Although the area had been Republican, he ran and won as a Democrat with Readjuster sympathies, and served from 1874–1880. He won re-election several times. During his last term, fellow delegates elected Lacy their 33rd Speaker. During that term, fellow legislators elected him, in 1880, to the Eighth Circuit Court to fill the seat vacated by Robert L. Montague, who had died in office. Lacy resigned his part time legislative position upon taking the trial court bench. J. Marshall Hanger, although of the opposing party, offered a resolution praising his faithfulness and integrity as Speaker. In 1882, the Virginia General Assembly elected four members to the Supreme Court of Appeals for twelve year terms effective January 1, 1883. Lacy, Thomas T. Fauntleroy, Drury A. Hinton and Robert A. Richardson remained on the appellate bench together until five successors took office in January 1895.
Death and legacy
During the final months of his term, Lacy suffered a lingering illness, and died at the age of 56 his New Kent County home, Marl Springs, on May 15, 1895. He was survived by his wife and four children, as well as his siblings, and buried at St. Peter's Episcopal Church.
