Mrs. Liu was a peasant. The driver of the BMW, Su Xiuwen, is the wife of a businessman. The initial scrape was minor, but after a confrontation, Mrs. Su drove the car into Mrs. Liu.
And that would have ended it, except for two things. First, the "BMW case" tapped into sharp class resentments emerging in this Communist country, which long espoused a classless society. And second, that anger was able to coalesce in what is becoming an increasingly influential court of appeals in China: the Internet, which boiled with online outrage.
This week, in a rare step, officials here announced an investigation into possible judicial corruption in the case, state media reported. There is already speculation that Mrs. Su could face a harsher verdict, a result that would appease the online critics but could also set an uneasy precedent for reformers trying to establish a genuine rule of law in China.
That yawning gap is a fundamental contradiction of China's economic boom. Wealth is pouring in, swelling the middle class, yet hundreds of millions still live in poverty.
Here in the northeast, once the country's industrial center but now mired in unemployment, it is not hard to find class bitterness rubbed raw by the case. "We ordinary people have to obey the laws," said a taxi driver. Mrs. Su, he said, does not: "She has the power. She has the privilege. She can drive wildly."
Initially, the accident barely attracted attention outside Harbin.
Then, after bystanders intervened, she returned to the car, apparently to back up. But she unexpectedly drove forward, crushing Mrs. Liu and injuring several others. The car crashed to a halt against a tree.
"My wife was dragged for six or seven meters," Mr. Dai said. He said he tried to lift her right arm but it was broken. He saw blood coming out of her mouth. "People said she was already dead," he recalled. "I was just dumbfounded."
The question at trial was whether Mrs. Su had intentionally tried to harm Mrs. Liu or had simply mistakenly put the car into first gear instead of reverse. The trial was notable for its lack of eyewitnesses, though many saw the incident.
One of them was Mr. Dai, who said he had received almost $10,000, roughly eight years' wages. He said he did not even attend the trial. "I just want peace for my family," a weary Mr. Dai said as one of his two daughters listened. "I don't care about the verdict and whether it is justice or not."
But China's "netcitizens" cared very much. Editors at Sina.com, the country's most popular Web site, said that after the verdict, more than 200,000 messages were posted to chat rooms, many suggesting corruption was to blame.