Mike Sheffield grew up watching "Perry Mason" and fulfilled a childhood dream of becoming an attorney when he graduated from the Emory University School of Law.

His online biography describes him as an aggressive criminal defense attorney with nine years experience as a prosecutor and 20-plus years as a defense counsel. It also states he prosecuted more than 3,000 cases and handled more than 300 jury trials.

The Atlanta native was known among colleagues for maintaining a cool head even in crisis, said Mike C. Murphy, a civil litigator who shared office space with Mr. Sheffield in downtown Lawrenceville.

"He was noted for his extraordinary, calm manner in dealing with criminal defendants," he said. "He was a professional, competent guy who handled situations and tried to do a good job. A hard-working guy."

Michael Sheffield of Norcross had a history of heart disease and at 42 suffered a heart attack. The defense attorney suffered a fatal heart attack Saturday while working in his office. He was 61.

A memorial service will be held at 11 a.m. Wednesday at Perimeter Church in Johns Creek. Crowell Brothers Funeral Home is in charge of arrangements.

Before going into private practice, Mr. Sheffield was an assistant district attorney for DeKalb County. He became a sole practitioner in 1999 and specialized in criminal law, DUI, traffic violations, felonies and juvenile criminal law.

In 2004 and 2008, he ran unsuccessfully for open seats on the state Court of Appeals. He thought he had made it to the runoff in his 2004 bid, but third-place candidate Howard Mead sued when he learned his name had been listed incorrectly on more than 400 ballots in Laurens County.

The state Supreme Court ordered a new election; in that race Mr. Mead made the runoff, not Mr. Sheffield.

"He was very disappointed," said Susan Sheffield, his wife of 18 years. "One neat thing about him was that he went out on his own to become a defense attorney when he was 50. Most people would just [stay] settled where they were at that age."

Last year, Mr. Sheffield, a card player and basketball fan, talked about what it was like running in a nonpartisan election for a post on a low-profile court.

"The problem is most people don't know much about the Court of Appeals or how it affects them, but it does affect them a great deal," he told The Atlanta Journal-Constitution. "Then you're trying to get your name out there without having to spend a semi-fortune, which is not easy to do."

Mr. Sheffield was a past president of the Gwinnett and DeKalb bar associations. He belonged to the State Bar of Georgia's Board of Governors and the Georgia Association of Criminal Defense Attorneys.

His brother, Ken Sheffield of Longmont, Colo., remembers a youngster who spent much of his time reading and engaged in "indoor activities."

"He was real studious growing up," his brother said.

Other survivors include his mother, Lucy Sheffield of Lawrenceville; a daughter, Olivia Sheffield of Norcross; and a son, Matthew Sheffield of Norcross.