Howard County Circuit Court Judge Robert F. Fischer thought he had heard every excuse that speeding motorists could contrive-until he heard the one about the rattlesnakes.

As C. Jay Kiessling described it, he was driving 70 miles an hour on I-70 last October because he thought the dozen squirming rattlesnakes in a bag on the back seat of his car might escape.

The snakes should have been in a wooden box, Kiessling explained, but when he picked them up at the Baltimore-Washington International Airport the box was damaged. So he threw the box away and decided to carry the snakes to the Maryland Reptile Institute of Ellicott City in the cloth bag that had been inside the box.

Kiessling, codirector of the Institute, said he was not very happy with that arrangement. But he was even less happy when he realized the sun coming through the rear windshield was making the back seat hot and the heat was making the snakes restless, he said. The thought of restless snakes made him nervous.

"Put it this way," Kiessling said yesterday. "If you had a bag of snakes in the back of your car, wouldn't you be in a hurry?"

The next thing Kiessling knew, he was stopped by a state trooper just after he passed a speed radar indicator. The trooper promptly gave him a $40 ticket for going more than 10 miles over the 55-mile an hour speed limit.

When the case came to District Court in February, the judge refused to accept Kiessling's explanation and fined him $45. Kiessing then appealed and, on Tuesday, Fischer proved to be more sympathetic.

"It seemed to me a normal person with moving rattlesnakes in the back of his car would be somewhat nervous," Fischer said after the hearing. He found Kiessling guilty but canceled his fine and ordered the charge stricken from his record.

"After hearing traffic cases for four years, when I had been a District Court judge, I never thought I would ever hear another original excuse," Fischer added. "But this testimony about the snake is a first."