BOSTON — The Lakers played their best defensive first half of the series when they held the Boston Celtics to 40 points on 40 percent shooting tonight in Game 3 of the NBA Finals. Ray Allen, who had 27 points in the opening half of Game 2, was scoreless on 0-for-3 shooting. Paul Pierce had only five points. Kevin Garnett finally showed up to the Finals and scored 15. Kobe Bryant led the Lakers with 16 points on 5-for-13 shooting. The Lakers led by as many as 17 points in the first half.