The Justice Department senior trial attorney who prosecuted both Rep. Charles C. Diggs Jr. (D-Mich.) on kickback charges and Korean businessman Hancho Kim for conspiracy in the Korea influence-buying case was awarded the department's distingusihed John Marshall Award for Trial Litigaiton yesterday.

Justice Department attorney John T. Kotelly, a nine-year evteran criminal prosecutor, was among the 242 Justice Department employes receiving awards in ceremonies yesterday in the department's Great Hall.

Kotelly obtained convictions on 29 counts against Diggs by a Washington jury, in October last year, on charges that Diggs-the nation's senior black congressman-inflated the salaries of his employes, portions of which were then funneled back to him to pay his personal bills.

Diggs, who has since resigned his chairmanship of the District of Columbia committee and the African affairs subcommittee, is appealing his conviction.

Kotelly was also the government prosecutor who investigated the socalled Koreagate case of influence buying in Washington. The investigation, which took Kotelly to Seoul for three weeks, ended in the May 1978 conviction of Kim for conspiracy and perjury. Kim is currently waiting to begin serving his six-month sentence.

The list of award winners and their achievements reads something like the 1978 almanac of famous criminal cases. Assistant U.S. Attorney Barry Leibowitz, who was shot in the back during an ambush in front of the D.C. courthouse last December, was awarded the Attorney General's Medal for his ongoing investigation of an international heroin ring.

The Attorney General's Award for Excellence in Law Enforcement was presented to Larry Wack, the New York FBI agent who identified three Cuban exiles charged with the 1976 bombing assassination of former Chilean ambassador Orlando Letelier and a business associate.

Also honored was Thomas P. Puccio, head of the Brooklyn Strike Force, for his investigation of another New York FBI agent on bribery charges. That agent, Joseph Stabile, pleaded guilty in Noveember to obstructing justice during the bribery investigation, and became the first active-duty FBI agent ever indicted.

The top awards were presented by Attorney General Griffin B. Bell and Deputy Attorney General Benjamin R. Civiletti. Highest honors-the Attorney General's Award for Exceptional Service and an accompanying check for $1,500-went to Deputy Assistant Attorney General John C. (Jack) Keeney, "in recognition and grateful appreciation of long and distinguished serviceexemplifying the highest standards of the Department of Justice."