SAN FRANCISCO — The U.S. attorney’s office has dropped a key witness from its economic espionage case against an Oakland engineer after the defense accused the China expert of plundering parts of his analysis from Wikipedia.

James Feinerman, a professor of Asian legal studies at Georgetown University Law Center, had been slated to testify about China’s efforts to steal technology from the West. But the government on Thursday rested its case against Walter Liew, who is on trial for allegedly selling details of DuPont’s manufacturing processes to China, without calling Feinerman.