ST. PAUL, Minn. (AP) _ The scenario was familiar enough: a fleeing vehicle, a police roadblock, cops shooting out the tires. The new twist was the speed - averaging 15 miles an hour - and an appeals court has thrown out the slowpoke's conviction.

The incident began last year, according to court documents, when farmer Jon Clifford Johnson finished planting soybeans at 1 a.m. and drove through Lakefield in his pickup, pulling a trailer.

Police Officer Ronald Morris followed Johnson, stopped him outside town and found that he did not have a driver's license. Johnson, 44, said he did not carry his wallet when he worked in the fields and did not intend to change that policy.

He drove away, saying he was heading home.

Morris followed in his cruiser with lights flashing and siren wailing.

Two other officers joined in the June 7, 1984, chase, with one officer shooting out two tires on the pickup truck, stopping Johnson about two miles down the road.

The Minnesota Court of Appeals concluded that the average speed of the chase was less than 15 mph.

''The record reflects not only poor judgment of a tired farmer but serious overreaction by the officers, leading to a road block and shooting out the tires of a slow-moving vehicle,'' a three-judge panel of the court said Monday in overturning Johnson's conviction for fleeing a police officer.

The court ordered a new trial, saying the original judge did not instruct the jury on the legal definition of intent.

Johnson's intent was crucial to deciding the case, the appeals court said. ''Johnson said he had a driver's license at home, and if Morris wanted to write a ticket, he knew where to find him.''