FLANDREAU, S.D. -- Rep. Bill Janklow, a dominating figure in South Dakota politics for nearly 30 years, was convicted of manslaughter Monday for speeding through a 'stop sign' at a rural intersection and colliding with a motorcyclist.

Janklow Manslaughter quickly announced that he will resign from Congress on Jan. 20 -— the same date he is scheduled to be sentenced. He could get up to 10 years in prison.

Jurors in the congressman's boyhood hometown convicted Janklow of second-degree manslaughter, reckless driving, running a stop sign and speeding for the Aug. 16 crash that killed Randy Scott, 55, a farmer from Hardwick, Minn.

Prosecutors said Janklow was traveling more than 70mph in a white Cadillac when he crashed with Scott's Harley-Davidson. "The state of South Dakota brought charges against a man we believed to be responsible for Randy's death," the victim's mother, Marcella Scott, said in a statement.

"We are satisfied that the correct verdict was reached." Janklow, 64, appeared stunned as the verdict was read.

He walked steadily out of the courtroom, got in a vehicle driven by his son and left the courthouse. He refused to respond to questions shouted by a horde of reporters.