Tommy Cross had not seen the video he recorded since New Year's Day. /*BART*/ police confiscated it soon after the shooting and declared it evidence.
Cameras were not allowed in the courtroom, but the video is clearer than others released to the media.
It shows /*Oscar Grant*/ seated on the platform, detained by officers. When he attempts to stand up, he is slammed to the ground. Officer Tony Pirone pins his head to the floor with his knee. /*Mesherle*/, standing over Grant's back, reaches into his holster, pulls out his revolver and fires.
After the shooting, Cross said he heard Mesherle say, 'Oh my God, oh my God.'
Cross wiped away tears as the video played. Grant's mother buried her head in her hands.
Attorney John Burris is representing Grant's family in a civil rights lawsuit against BART.
"We believe that significant evidence has been presented as it relates to a holding for murder," Burris said. "The defense will now put on their case and they will do what they can to reduce it from murder to some other degree."
Mesherle walked into the courthouse Tuesday under tight security.
Attorney Michael Cardoza said the evidence so far hurts the defense's case.
"I really don't believe they think that they can overcome the evidence that's been put into this to this point," Cardoza said.
Jamil Dewar was with Grant that night. The defense questioned the 16-year-old about how much Grant had to drink and whether he escalated a fight on the train before officers arrived.
"The defense has no choice but to try to demonize Oscar, but the video speaks for themselves," Grant's uncle Bobby Johnson said.
Prosecutors also put BART passenger Daniel Liu on the stand to question him about a video he recorded. He testified that Grant repeatedly moved his left hand while officers tried to get both hands behind his back. Wednesday the defense begins its case.