Setting aside the parents, nobody would defend that suspect.
Literal
Parents [topic-は] setting-aside, nobody that suspect [object-を] defend-not would.
~はさておき means 'setting aside X' or 'leaving X aside for now' — acknowledging an exception before making a general claim. ~ないであろう is a formal/literary negative conjecture: ない + であろう. 容疑者 (suspect) and 弁護する (to defend) are legal vocabulary.