A federal judge shot down BP's request to penalize Halliburton for allegedly destroying damaging evidence about the quality of its cement slurry that went into drilling the oil well that blew out last year and caused the nation's worst offshore oil spill. BP did not prove that it had been "prejudiced" by Halliburton's actions, U.S. Magistrate Judge Sally Shushan wrote in a ruling...But Shushan told Halliburton to turn over a computer that ran tests on the cement slurry. The judge ordered a third party to run forensics tests on the computer to see if data Halliburton says was lost can be retrieved...BP...and its two main contractors on the ill-fated well, Halliburton...and Transocean...have been sparring in advance of a trial that starts Feb. 27. U.S. District Judge Carl Barbier will decide fault for the spill in the first phase of the non-jury trial. BP accused Halliburton employees of doing an internal investigation and discarding and destroying early test results after the blowout that found problems with the cement slurry.