At hearing Wednesday, attorneys argue whether his actions the night Oscar Grant was killed constituted 'gross negligence' required for his manslaughter conviction  

The Oscar winner in line to play Grant's mother  

Johannes Mehserle, in a letter to the public released today, says he is sorry for the shooting that took Oscar Grant's life, wishes he could speak to Grant's family members and describes the moments after the shooting on the Fruitvale BART station platform on Jan.1, 2009.