If someone were to simply use a single-word interrogative at the end of a sentence, then it would be preceded by a comma, like so:
You were there the night of the murder, right?
But suppose the speaker says the following:
You were there the night of the murder [punctuation here] is that correct?
I know that a semicolon would not be suitable here, so that leaves either a comma or a period. I'm leaning towards a period, but some people have told me to use a comma. I'm a little skeptical about that advice.
What punctuation should be used in a multi-word interrogative at the end of such a sentence as the one above?