Florida teenager Trayvon Martin can help prove he was killed "in cold blood" by George Zimmerman, a neighborhood watch volunteer, an attorney for Martin's family said Tuesday. The girl, who was dating the 17-year-old, "completely blows Zimmerman's absurd self-defense claim out of the water," lawyer Benjamin Crump told reporters. The girl -- who he said does not wish to be identified -- "connects the dots" about what happened that day when she lays out what she overheard while on the phone with him, he said. 911 calls paint picture of chaos