In a criminal case, do witnesses who testified at the trial testify all over again at the appeal?

There is not testimony in appellate matters. The appellate court will rely, as necessary, on the transcript from the trial court. The appellate court will also rely on briefs (written arguments) filed by the parties (in this case the Defendant and the State), and oral arguments made by the parties.

No. An Appeal is based on what occurred at the Trial. Transcripts of the Trial are ordered by the Appellate Attorney and attached to the Appellate Brief.

As stated in the previous answers there is no testimony taken in an appeal generally. The appeal is limited to a review of the transcripts of what took place at the hearings and trial. As a general matter there are rules specifically limiting the appeal to scope of the record from teh court below. The only time any "new" testimony is ever taken is if the appellate court should for some reason remand the case back to the trial court for the purpose of conducting an evidentiary hearing of some sort. Then and only then does the record on appeal get expanded to include the original trial transcripts as well as the transcripts from such a hearing.

The only time witnesses will testify again is if you win your appeal and have to have the case tried again. Then, in that instance, they must all do it again, or at least most of them. Otherwise, there is no testimony taken in appeals. Its all based upon the record of the trial itself and legal arguments about what happened during the trial and why it should be overturned.