Judge Leighton was born George Neves Leitao, the son of Anna Silva Garcia and Antonio Neves Leitao, natives of the African-coastal Cape Verde Islands. He was reared in Massachusetts, in New Bedford and on Cape Cod, and attended grade schools in both places. During his childhood, he worked as a berry picker, then as a dishwasher and cook. In the year that he began the seventh grade in public school, he left school to take a job on an oil tanker sailing to the Dutch West Indies, ending his public school education. Between that time and September of 1936, Judge Leighton read extensively from books he borrowed from various sources, attended night schools, and studied in Works Progress Administration classes.
In the winter of 1935, as a memorial to those who had died in the collision of the USS Nantucket with the SS Olympic, the Cape Verdeans of New Bedford created the Cape Verdean Memorial Scholarship Fund. In 1936, the first essay contest was held and two prizes were awarded for the best essays submitted. The two prizes, each for $200.00, were to provide initial tuition for the winners in any college of their choice. Judge Leighton won one of the awards. Although his application for a scholarship to Howard University was rejected, he was informed by Mr. F. D. Wilkinson, then Registrar of the University, that he could attend Howard as an unclassified student, and if he proved he could do college work without having attended a high school, Howard University would make him a candidate for a degree.
Leighton accepted the challenge. At the end of his first semester examinations, he made the Dean's Honor Roll, and remained in that status through four years of college studies, despite working a variety of menial jobs. As a consequence, he was made a candidate for a degree in the College of Liberal Arts and graduated in 1940, magna cum laude. He enrolled in the Harvard University School of Law in September 1940. His law studies were interrupted by active duty in World War II. While in the military, Judge Leighton was decorated with the Bronze Star. He returned to Harvard in October of 1945 and received his LL.B. degree on November 25, 1946.
In 1951, together with the late Loring B. Moore, Judge Leighton founded the law firm of Moore, Ming & Leighton, predecessor to the law firms of McCoy, Ming & Leighton and McCoy, Ming and Black. In 1964, Judge Leighton began his judicial career. He was a Judge of the Circuit Court of Cook County, Illinois from 1964 to 1969, and a Judge of the Appellate Court, First District, from 1969 to 1976.
Judge Leighton was appointed to the United States District Court for the Northern District of Illinois in 1976, by President Ford. He served on the District Court from 1976 to 1986, taking senior status in 1986 and retiring in 1987 to become Of Counsel to the Chicago law firm of Earl L. Neal & Associates.
Judge Leighton was the first African-American lawyer to sit on the Board of Managers of the Chicago Bar Association, the first African-American judge to serve as a Chancellor in the Circuit Court of Cook County and the first African-American judge to sit on the Illinois Appellate Court.
Also, for twenty-seven years, Leighton has been a professor of law at the John Marshall Law School. Teaching, along with being a lawyer and a judge, has been a source of great satisfaction for him over the years.
Judge Leighton believes that aspiring lawyers and judges must have within themselves a high standard of personal achievement which can function as a bulwark against the many temptations that confront lawyers and judges. The bulwark, he suggests, should then be perfected "with study, the love of learning, and high standards of personal performance at all times in all things and in all ways."