Representative William J. Janklow of South Dakota was charged today with second-degree manslaughter in the death of a motorcyclist who was struck his car in an accident on August 16.

The prosecutor in Moody County, S.D., Bill Ellingson, said the manslaughter charge, a felony, implied “more than ordinary negligent conduct” and carried a maximum punishment of 10 years in prison and a $10,000 fine.

Mr. Ellingson said he had ruled out an even more serious charge, vehicular homicide, since there was no evidence that Mr. Janklow was under the influence of drugs or alcohol at the time of the accident. Witnesses said his car had run a stop sign at a rural intersection and struck the cycle driven by the deceased.

The congressman suffered a head injury and a broken hand in the accident. His son, A. Russell Janklow, a lawyer in Sioux Falls, S.D., has described his father as deeply distressed over the death of Mr. Scott. The congressman’s office said today that it did not have an immediate comment on the charges.

Janklow, 63, also faces three nonfelony charges: speeding (driving 71 miles per hour in a 55-m.p.h. zone), failure to stop at a stop sign and reckless driving. The first two charges are punishable by up to 30 days in jail and fines of up to $200 upon conviction. Reckless driving carries a maximum one-year jail term and $1,000 fine.

The accident that killed Mr. Scott on Aug. 16 was the latest and most serious of a series of traffic mishaps involving Mr. Janklow, who has acknowledged having a heavy foot on the accelerator.

Newspaper reports in South Dakota said Mr. Janklow had been involved in seven previous accidents in the last 10 years, one that resulted in minor injuries, and was cited at least 12 times from 1990 to 1994 for speeding violations, some for exceeding the limit by 20 m.p.h. or more.