Present participle of 'depone': the act of giving testimony or making a formal statement under oath.
From 'depone' with the present participle suffix '-ing.' It describes the ongoing action of testifying or formally depositing a statement.
In Scottish law especially, 'deponing' is used as a noun to refer to the actual process of testimony, whereas in American English we'd more commonly say 'testifying' or 'giving a deposition.'
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