Is secretly recording the voice of one's maternal aunt to prove innocence from her accusations considered unlawful (haram)?

If you recorded what transpired between you and your maternal uncle's wife without her knowledge, in order to clear yourself from a false accusation, there is no blame upon you for that. This is supported by the permissibility of a hidden witness's testimony according to many scholars, as it is permissible for one who has a right against a person who denies it openly, to bring witnesses who conceal themselves to listen to their confession and bear witness to it. Ibn Qudamah permitted this testimony, indicating that it is permissible for someone who openly denies a right but admits it secretly. Al-Zarkashi clarified that this does not fall under the prohibition of espionage, because it is permissible due to the necessity that calls for it.