It’s very common for lawyers to talk about “deposing” a witness, as if the lawyer were the one doing the deposing; and the press has picked this usage up. We see today, for example,
Infowars host Alex Jones to be deposed in defamation suit brought by Sandy Hook parentsHeadline, NBC News, 14 February 2019
Judge rules Sandy Hook families can depose Alex Jones in defamation caseHeadline, The Hill, 14 February 2019
This is not at all surprising, and one could argue that it’s correct, since that’s the way most people say or write it. Historically, however, it’s wrong.
The verb, to depose, derives from the Latin, depono, meaning to put down. In the context of testimony, it’s the witness, not the lawyer, who deposes. (To depose a person generally means to force him or her from an office or station.)
This is reflected in the language of affidavits and certificates in most Common-Law jurisdictions, where the affiant, “being duly sworn,” almost universally “deposes and says” whatever she or he has to say.
I won’t say that people who claim to depose witnesses are wrong, exactly, but I would encourage them to take the deposition of the witness (which is also still current) instead.