Non-responsive (mostly) home button. Broken button or dock connector?

My home button is mostly non-responsive (occasionally it works when pressed, usually nothing happens).

Is there any way to tell, prior to disassembling the phone and replacing either the button or the dock connector (or both), which part is to blame?

I've not noticed any speaker, charging or sync issues.

Thanks.

Background info: the phone also has the faulty secondary mic problem (no audio on speakerphone, Facetime or video recordings; audio fine on regular calls, headset calls, voice memos and other apps like Soundhound. No debris in top mic hole.) I always wondered whether these problems were related via the dock connector, or whether I'm just unlucky.