If I were preparing a defence, and there were several reasons why I was innocent, why should I be required to pick just the one? I think a defence of
1) I was out of the country,
2) that picture looks nothing like me,
3) the person sounds nothing like me, and
4) you are also out of time for prosecuting me,
would look pretty convincing. I wouldn't like to decide which of those to pick if taken to court.