WASHINGTON (Reuters) - Democratic lawmakers on Tuesday blasted police handling of a racially charged case in which a neighborhood watch volunteer shot dead an unarmed black teenager in Florida, accusing local law enforcement officials of botching the investigation. The lawmakers, speaking at a congressional forum attended by the parents of the slain teenager, called for the immediate arrest of 28-year-old George Zimmerman, the white Hispanic who shot 17-year-old Trayvon Martin on February 26 in what Zimmerman said was self-defense. ...