1
general::
Phrase(s): beside the point [and] beside the question
irrelevant; of no importance. • That’s very interesting, but beside the point. • That’s beside the point. You’re evading the issue.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, beside the mark or question. Irrelevant, off the subject. For example, Whether you had insurance is beside the point; the accident is your fault. These terms came into common use in the mid1800s. Also see NEITHER HERE NOR THERE.
American Heritage Idioms