PRETORIA, South Africa — A shaken Oscar Pistorius refused to look at a gruesome photo of his slain girlfriend's bloodied head on Wednesday, telling a prosecutor through tears, "I don't have to look at a picture. I was there." "It's time that you look at it," chief prosecutor Gerrie Nel said during a fierce first day of cross-examination in which he doggedly pressed the double-amputee Olympian to "take responsibility" for killing Reeva Steenkamp.