The flag flew at half-mast yesterday at Freestate Raceway where shock and tributes continued to be expressed following the death of Fulton Wayne Smullin, 41, the leading trainer-driver on the Maryland harness circuit.

Mr. Smullin died late Friday night from head injuries he suffered in a ninth-race accident at the track Thursday night.

Mr. Smullin suffered trauma of the brain, a fractured skull and fractured ribs in a three-horse accident. It occurred after the horse he was driving broke stride and his sulky was rammed from behind by another horse. His horse somersaulted and Mr. Smullin became jammed against the sulky and his horse, in the fall to the track.

He was rushed to Greater Laurel-Beltsville Hospital, then transferred to the Prince George's General Hospital shock trauma unit where he was placed on a life-support system.

"He (Mr. Smullin) meant everything to Maryland racing," said Harold Frazier, a former driver and now the local representative of the Cloverleaf Standardbred Owners Association. Frazier had known Mr. Smullin 18 years.

"He gave it integrity and class," Frazier said. "A man everybody looked up to and respected. He helped everybody.

"He lived to be a driver. That was his objective all his life. His mother told me that ever since he was 9 he wanted to drive."

Frazier said he hopes Cloverleaf will look into the improvement of safety equipment used by the drivers, especially the helmets.

John Lare, one of the leading trainers in Maryland, used Mr. Smullin as his driver until a broken leg last winter sidelined Mr. Smullin.

"The man was the fairest guy we had here in the business," said Lare.

After the accident, when it became apparent Mr. Smullin would not survive, Lare talked to the owners he works for, and they decided to donate any purse winnings from Lare's five starts Friday night to Mr. Smullin's son David, 16, to help with his education. Lare-trained horses won four races, with winnings surpassing $7,000.

Although aware of the dangers on the track, Mr. Smullin never feared driving, according to his wife of the past 10 years, Jacqueline.

She recalled Mr. Smullin telling her, "If you were afraid of driving, you couldn't make the moves you have to to win."

Mr. Smullin began driving in 1969, when he won six races in 42 starts. He accumulated more than 1,500 victories for earnings of $4 million. In 1981, he had 276 victories and was ranked 12th nationally.

Last year he was ranked 20th in the nation with 244 victories and earnings of $806,785. The leading driver at the current Freestate meet, Mr. Smullin had 88 victories, twice those of his closest pursuer.

Mr. Smullin was the first standardbred handler to die as the result of injuries in a Maryland harness race, and the first nationally to lose his life in nearly a year.

Shelly Goudreau of Canada died six days after being thrown from his sulky at Hollywood Park on Aug. 27, 1982.

The last death in Maryland horse racing came in 1978, when jockey Robert Pineda was killed in a race at Pimlico. Jockey Happy Witner was killed at Timonium in the 1950s and Bernard (Buddy) Handford lost his life at Pimlico in 1933.

Mr. Smullin is survived by son David; a brother, Frank Jr.; two sisters, Norma Jean Murray and Rita Churn, and parents, Virginia and Frank Sr.

Funeral arrangements are incomplete. Mr. Smullin will be buried in Onancock, on Virginia's Eastern Shore. A memorial service is planned at or near Freestate, although arrangements are not definite.