Defense laywers in the bribery trial of former D.C. Superior Court judge Robert H. Campbell yesterday successfully blocked prosecutors from showing the jury a massive computer study of the thousands of local traffic cases which the government contends contains "compelling evidence" that Campbell gave favorable treatment to a local construction firm.

U.S. District Court Judge Thomas A. Flannery's decision sustaining defense objections to the study was viewed as a stiff blow to the government's efforts to prove that Campbell gave lenient sentences on overweight truck tickets issued against the firm in exhange for more than $10,000 in cash and various gifts and services.

Flannery ruled that whatever value the study might have as evidence against Campbell was outweighed by the danger that it could confuse and mislead the jury and be unfairly prejudicial to him.

The computer study covered more than 90,000 traffic cases that came before Campbell from December 1974 to June 1977, while he was on the Superior Court bench, including 8,690 cases that came before him for sentencing. Thousands of other cases were disposed of prior to sentencing, usually through dismissal or a driver's decision to forefeit collateral.

The government wanted to compare the sentences Campbell imposed on the construction firm, Excavation Construction Inc., for overweight tickets to the sentences he imposed on thousands of other cases, the vast majority involving parking violations.

Prosecutors contended that although parking violation penalties generally are less severe than those for overweight trucks, the study showed Campbell nevertheless imposed many jail terms and heavy fines in parking cases while suspending or delaying imposition of sentences in the overweight truck cases involving Excavation Construction. o

Flannery said, and the government conceded, that it would have been better to compare Campbell's handling of Excavation's overweight tickets to overweight tickets issued to other firms. Assistant U.S. Attorney Carol E. Bruce told Flannery that that such a comparison could not be carried out on the Superior Court computer.

Flannery said the government could not be faulted for the shortcomings of the court's computer system. But at another point, he told Bruce he was not impressed by the government's contention that it would have been difficult and extraordinarily time-consuming to check the court records by hand.

"It is the government's obligation to prepare its case and if it's difficult, that is just too bad," Flannery told Bruce.

Without the computer study, the government is expected to use the testimony of witnesses to try to prove its charge that Campbell acted favorably toward Excavation Construction. Yesterday, the government also began to introduce into evidence the actual traffic court files for Excavation Construction that show how Campbell disposed of those cases.

In addition to the former judge, the construction firm's general manager, Larry A. Campbell (no relation to the judge) and the firm itself are all on trial for conspiracy, bribery and racketeering.

During the last week, the jury of eight women and four men has heard complex financial testimony from federal agents who examined both Campbell's personal bank records and records from Excavation Construction. The government is attempting to demonstrate that unexplained deposits were made in Campbell's bank accounts near the time that moeny was withdrawn from construction company accounts, money the government contends was used to bribe Campbell.

The trial will resume Monday.