How does a defense lawyer unwind after beating 13 of 14 counts in the biggest trial of his career? "I'm going to play poker tonight," said R. Kenneth Mundy, smiling coolly.

"And he's going to win!" added an exuberant Anita Bonds, who had assisted Mundy in his defense of Mayor Marion Barry and was Barry's campaign manager until he canceled his reelection bid.

About an hour after the jury declared it was hopelessly deadlocked on most of the drug and perjury charges against the mayor, Mundy treated the staff of his law office to $70 worth of drinks (including two bottles of champagne) at the Madison Hotel downtown.

And Mundy seemed to be the most laid-back of the 10 people there. One woman, spreading the news of the mistrial -- loudly -- by portable telephone, took a moment to tilt her head back and pump her fist in the air victoriously.

With the white collar of his otherwise pink shirt unbuttoned, Mundy cheerfully rejected the suggestion that this was the biggest night of his professional life. What possibly could have topped it? "The first case I won, which was a drunk driving case," Mundy said. That was 25 years ago. "I won that case, and that was the biggest night of my professional life," he said, laughing heartily.

All the while the jury deliberated, "I wasn't thinking about the case, really, because I was wrapped up in other work," Mundy said. "We're getting ready for three or four major trials this fall. And that's where our energy has really been devoted. I thought {the deliberations} would take a while."

When Mundy got a call yesterday afternoon informing him that the jury had passed a note to the judge, he didn't suspect that the trial was about to end. "We've had so many false alarms. We've had so many messages already," he said. "This was a terrible burden, just running back and forth to court."

So does Marion Barry owe Ken Mundy a dinner now or what?

"The mayor is a fine person. He doesn't owe me a dinner," the lawyer said. Then, after a couple of seconds: "He owes me his life! No, no, I'm kidding," Mundy said, laughing. "Don't print that."