Nephi even predicts that the murderer will do two things: he will say that Nephi had nothing to do with the crime, and then testify that Nephi is a prophet of God:
“And then shall he say unto you, that I, Nephi, know nothing concerning the matter save it were given unto me by the power of God. And then shall ye know that I am an honest man, and that I am sent unto you from God.”