What is the legal test for a motion to exclude the testimony of a witness under the Fifth Amendment?

"... [D]efendants must allege a violation of their own rights in order to have standing to argue that testimony of a third party should be excluded because it is coerced. It is settled that the accused has no standing to object to a violation of another's Fifth Amendment privilege against self-incrimination." (People v. Badgett (1995) 10 Cal.4th 330, 343.) "... [T]here is a significant difference in the burden of proof applicable to a claim under the Fifth Amendment and defendants' claim that the testimony of a third party is subject to exclusion as a matter of due process. The burden is on the People to demonstrate the voluntariness of a defendant's admissions or confessions by a preponderance of the evidence." (Id. at p. 348.) "By contrast, when a defendant makes a motion to exclude coerced testimony of a third party on due process grounds, the burden of proving improper coercion is upon the defendant." (Ibid.)