I've heard of the adjectives 'nonresponsive' or 'unresponsive', but are they restricted to law^?
Collins Dictionary: nonresponsive = not responsive, not reacting to a stimulus
The definition above differs from the definitions of adjectives like 'equivocate, evade' and nouns like 'dodging', but these are negative and accusive; I prefer neutral connotation.
^Only if you wish, please see: http://law.indiana.edu/instruction/tanford/web/reference/objections.html, p 169 of The Trial Lawyer: What it Takes to Win by David Berg,
p 271 of Trials: Strategy, Skills, and the New Power of Persuasion by Thomas A. Mauet.