Who bears the burden of proof regarding the timing of an accusation of defamation (Qadhf) relative to marriage?

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If a woman claims she was defamed by a man before he married her, and the man claims the defamation occurred after the marriage, the statement of the man is accepted. Similarly, if a woman claims she was defamed after divorce (*bainunah*), and the man claims it was before the divorce, the man's statement prevails. This is established because the default ruling regarding the act of defamation itself rests upon the man's assertion; therefore, the timing of that act also rests upon his assertion.