It seems obvious to me that a judge should be present during voir dire and trial. Its so black letter that when questioned about what that really means no cases or statutes come to mind.

Does anyone know a line of cases that address issues like leaving the bench for brief periods of time without recessing court?

What? While a jury is in the box? While a witness is on the stand? I can think of one we lost where the judge dozed momentarily during a revocation. Turner v. State, Nos. 05-01-00299-CR, 05-01-00300-CR, &05-01-00301-CR, 2002 Tex. App. LEXIS 7135 (Tex. App.--Dallas Oct. 9, 2002, no pet.).

No, no, its not that bad. I was just asked to look into the issue of when a judge absolutely must be on the bench.