He worked as an attorney for the Atlanta Legal Aid Society in 1967. He served as an assistant district attorney of Fulton County in 1968 and from 1970 to 1975. Cooper then served as a judge on the City of Atlanta Municipal Cour from 1975 to 1980. Cooper was the first African-American appointed to a full-time judgeship on the Atlanta Municipal Court[citation needed] and the first African-American ever elected to a county-wide judgeship on the Fulton Superior Court[citation needed]. He was also the first African American assistant district attorney hired to a State Prosecutor's office in Georgia in 1968[citation needed]. Judge Cooper was the presiding Judge in the trial of Wayne Williams, the prime suspect in the Atlanta child murders, who was convicted of the murders of Jimmy Payne and Nathaniel Cater. He was a judge on the Fulton Superior Court, Georgia from 1980 to 1990. He was a judge on the Georgia Court of Appeals from 1990 to 1994.
This section needs to be updated. Please help update this article to reflect recent events or newly available information.(April 2015)
Cooper was assigned to the case of Whitaker v. Perdue, a federal challenge to Georgia House Bill 1059 which requires that registered sexual offenders cannot live or work within 1,000 feet from schools, school bus stops, churches, day care centers, and areas where children gather, such as parks, recreation centers, playgrounds, swimming pools, etc. In July 2006, Judge Cooper issued a restraining order barring enforcement of the law near the vicinity of bus stops. In August, he certified a class-action lawsuit on behalf of all of Georgia's 11,000 registered sex offenders instead of just the eight plaintiffs. On March 30, 2007, the judge dismissed some of the plaintiff's claims from the suit, including the claim that the law represented cruel and unusual punishment; the rest of the case will go forward. Plaintiff's lawyers had until June 1, 2007, to file a new, revised complaint.[citation needed]
Judge Clarence Cooper Judicial Section Award (this award is given to jurists for outstanding service to the judiciary and the community).[clarification needed][citation needed]