Former D.C. Alcoholic Beverage Control Board chairman Robert C. Lewis, on trial in U.S. District Court on charges of conspiracy and bribery, took the witness stand in his defense yesterday and acknowledged that he sought to help bar owner Tommy M. Motlagh obtain a liquor store lease at Hechinger Mall.

Yesterday's court session ended before Lewis was asked the key question of whether he and his former top aide, James E. Boardley, sought to share in the liquor store's profits.

Lewis, who also formerly was head of the city's Licenses, Investigations and Inspections department, said he assisted Motlagh, whom he called a personal friend, in efforts to obtain a lease for a liquor store at the mall in Northeast Washington as well as in efforts to finance the store through a city-funded housing agency.

Lewis also acknowledged taking a gambling trip with Motlagh to an Atlantic City casino in October 1980, but denied the prosecution's contention that he allowed Motlagh to pick up the tab.

Lewis, Boardley, and Motlagh all are charged with bribery and conspiracy in an alleged scheme to secure a lease at the mall for Motlagh and guarantee him a license to operate a liquor store there in exchange for a share of the store's profits.

Government prosecutors have played for the jurors several secretly taped conversations in which Lewis and Boardley say they expected 3 percent to 5 percent of the store's profits and that they could guarantee a liquor license for Motlagh despite anticipated community protests.

Defense attorneys have contended that the two officials were entrapped into making statements about "an arrangement" with Motlagh, and that the ABC regulations they are accused of abusing are open to interpretation.

Lewis, who has been running a service station since he was dismissed from his city post last year, yesterday discussed his friendships with Motlagh and Boardley and how he came to be involved in what the defense contends was an innocent effort to help a businessman. His version of the events stuck closely to evidence introduced by government prosecutors, but differed significantly on crucial points.

Lewis acknowledged making repeated efforts to put Motlagh in touch with someone at Hechinger who could speak with the bar owner about acquiring a lease on a liquor store in the then-new mall.

A Hechinger real estate representative has testified that Lewis called her beginning in mid-December 1979, but Lewis said his inquiries began only after Boardley had introduced him to Motlagh early the next year at an ABC hearing.

When his efforts failed to produce a letter to Motlagh initiating discussions on a lease, Lewis said he called the company's vice president for construction, with whom he had worked as a city architect, to arrange a meeting to discuss the store.

Boardley has said on one of the tapes that his relationship with Motlagh was "more a friendship thing, than an investigator and a licensee." Lewis testified that following hearings in early 1980 on Motlagh's Northwest Washington go-go club, the Godfather, which Motlagh wanted to sell, his professional relationship with the prospective liquor store owner became one of friendship.

They dined out many times together, Lewis said, and also visited each other's homes. It was at O'Donnell's Sea Grill resaurant in Bethesda, Lewis testified, that he, Boardley and Motlagh met with Abraham Beaton Jr., president of the city-funded D.C. Development Corporation, to "see if Beaton could assist in arranging financing" for the store.

Beaton, Lewis said, had an uncle who had a bank at Hechinger mall and who might assist Motlagh in obtaining a lease there. "I know that Mr. Beaton said he would help," Lewis said.

Beaton has testified that he left the meeting after Motlagh picked up the $74 restaurant tab and never discussed the matter with the men again. Lewis confirmed on the stand that he had no further conversations on the matter with Beaton.

In October 1980, Lewis said, he, Boardley, Motlagh and another man drove together to Atlantic City. "My wife thought it might be a good idea to get out of town. I had been working hard. I was irritable, cranky," Lewis testified.

He said he took $400 with him and lost most of it at the casino's gambling tables the first day. He acknowledged signing bar checks under Motlagh's name.

"He Motlagh told me if I needed anything or wanted anything, to sign his name and I could reimburse him . . . I asked him while checking out what was my portion of the bill. He said we'd figure it out later."

He said he later gave Motlagh $100 and Motlagh accepted it. He didn't learn until last week in the courtroom, Lewis said, that Motlagh received free rooms, meals and drinks as a "preferred customer" of the casino.

In December of that year, Lewis and Boardley met with Hechinger Co. executive Daniel Russell at the Flagship Restaurant to discuss the possibility of Motlagh's leasing a liquor store at the mall. Lewis said he didn't see Russell again until Jan. 22, 1981, after Russell had gone to U.S. prosecutors saying he felt Boardley had threatened him with delays in the mall project if Motlagh were not granted a lease.

Lewis said that in the meantime he learned in conversations with Boardley that "Russell was willing to help" but that he also "wanted something out of it."

They met at Lewis' house in Northwest Washington. Russell brought a friend and representative named "Wade McKeever," who was in reality an FBI agent recording the conversation with a concealed microphone.

Lewis is scheduled to resume testifying this morning.