What is the test for determining whether a witness has a valid Fifth Amendment right not to testify?

On the merits, the court's instruction correctly recited a broad legal principle, but was arguably too general or incomplete as applied. CALCRIM No. 320 is based on the following principles: "When a 'court determines a witness has a valid Fifth Amendment right not to testify, it is . . . improper to require him [or her] to invoke the privilege in front of a jury; such a procedure encourages inappropriate speculation on the part of jurors about the reasons for the invocation. An adverse inference, damaging to the defense, may be drawn by jurors despite the possibility the assertion of privilege may be based upon reasons unrelated to guilt. . . . But where a witness has no constitutional or statutory right to refuse to testify, a different analysis applies. Jurors are entitled to draw a negative inference when such a witness refuses to provide relevant testimony.' " (People v. Morgain (2009) 177 Cal.App.4th 454, 466 (Morgain); see People v. Lopez (1999) 71 Cal.App.4th 1550, 1554 (Lopez).)

Applying Morgain and Lopez, the court in People v. Sisneros (2009) 174 Cal.App.4th 142 (Sisneros) found the jury could permissibly draw a limited evidentiary inference from a gang associate's refusal to be sworn or testify in the defendant's trial when she had no legitimate right to refuse to testify. (Id. at pp. 151-152.) The court permitted the jury to consider the associate's refusal to testify for the limited purpose of supporting an expert's opinion regarding gang retribution, where the expert was familiar with the associate and had a credible basis for opining that the associate was refusing to testify for fear of gang retribution. (Id. at pp. 152-153.)