How can you still be charged for first degree murder?

While a body is important to be charged with murder it is not required if the Government can establish the person in fact died. it would be an important issue at trial. A body can help determine cause and time of death. The government then ties those facts to the defendant and other physical evidence. if there is no body the government might rely on witnesses's, forensic evidence such as blood, statements of the accused etc. Not having a body can make it more difficult a good example is the Scott Peterson case in California.