The autobahn speeder known as Turbo-Rolf, who contributed to the death of a young woman and her daughter, was jailed for 18 months today.

The verdict ended a trial which has stirred passions across Germany, even resulting in death threats against the judge, Brigitte Hecking, apparently from a person or a group sympathetic to the man who was driving at over 155mph at the time of the crash.

Rolf Fischer, a 34-year-old test driver for DaimlerChrysler, looked pale and shook his head repeatedly after Judge Hecking found him guilty of manslaughter. "There has never been a car accident in the modern history of Germany that has so aroused popular feeling," said prosecutor Matthias Marx.

He had demanded a 21-month sentence - in part as a signal to other high-speed tailgaters on the motorway network - but will probably not lodge an appeal. The defence is demanding a retrial.

Herr Fischer, said the judge, had been speeding legally down the fast lane of the A5 - most stretches of the German Autobahn have no upper speed limits.

He flashed the car of the 21-year-old mother who was accompanied by her two-year-old child, and signalled that he wanted clear passage. "It was a driving manoeuvre that occurs hundreds of times a day," said the Tagesspiegel newspaper today.

"It usually works out alright because the driver in front keeps his nerve and switches lanes without panicking. But on July 14, 2003, it all went wrong."

The woman lost control of her car and crashed fatally into some trees. Herr Fischer, said the judge, drove on.

Later he rang the police to ask details of the accident. This aroused initial suspicions.

Four witnesses were heard and it quickly became clear how difficult it is to judge visual testimony in high-speed cases. One witness identified Herr Fischer’s car, a Mercedes CL600 Coupe, on the basis that it had two separated headlamps on either side.

But the witness himself was travelling at 158mph and was being overtaken; his observation was based on a split-second assessment.

There were two test drivers on the stretch of motorway at the time. One was Herr Fischer’s boss, driving a Mercedes S Class. This prompted speculation that the employee could somehow have been covering for his boss, but the judge was ultimately convinced by the witnesses. Much of the questioning hinged on whether the witnesses could tell the difference between the two models of Mercedes.

The jail sentence - which will have to be served out and will not be suspended - is strict by German standards. Even so, said Rainer Bogs, spokesman for the Karlsruhe prosecutor, the "fast lane tailgaters on German Autobahns will not be deterred. We must still reckon with irresponsible overtaking hundreds of times a day."

Two wooden crosses, a smaller one representing the infant daughter, have been planted on the accident site. The family of the dead woman left the courtroom today to place flowers on the Autobahn crash scene.