The presiding judge may not testify as a witness at the trial. A party need not object to preserve the issue.
N.H. R. Evid. 605
2016 NHRE Update Committee Note
This rule was adopted by supreme court order dated April 20, 2017, effective July 1, 2017. The Committee recommended adoption of this rule, because it believes that it states the obvious, and there does not seem to be any reason to continue to exclude it.