Katie Holmes was a surprise spectator at Queens Supreme Court in Kew Gardens yesterday, listening to the opening statements in an alleged shaken baby death case. The Post’s Christina Carrega reports a fresh-faced Holmes listened intently as prosecutor Leigh Bishop made her opening argument in the case against Hang Bin Li, who is accused of violently shaking his 2-month-old baby Annie Li to death in 2007. Li is facing 25 years to life for murder and endangering the welfare of a child. He denies the charges. Holmes, the new famous face of Bobbi Brown cosmetics, graced the courthouse in a conservative outfit and no makeup. She came with an unknown companion to lend support to her pal Bishop, according to the star’s reps. Her spokeswoman told us, “She was there supporting her friend who is the prosecuting DA.” Witnesses said Holmes leaned in to listen to Bishop and Li’s attorney Cedric Ashley during their opening arguments from the back of the courtroom, and then quickly left.