In a comment to my prior post, SMilani noted that the relevance of her testimony would depend on her having prior contact with Tsarnaev, and that turns out to be correct.  Paul noted that her hearsay rendition of Tsarnaev's statement looks like the state-of-mind exception to the hearsay rule.

Doug Berman notes in a comment that the rules of evidence do not apply in sentencing proceedings.  That's a bit overstated.  It varies by jurisdiction, and capital cases are not necessarily the same as sentencing proceedings generally.  The rules of evidence do apply to penalty phase proceedings in California capital cases.  See People v. Richardson, 43 Cal. 4th 959, 1033, 77 Cal. Rptr. 3d 163, 221-22, 183 P.3d 1146, 1195 (2008).  I don't know about federal cases, though.

In any event, this part of the testimony may have barely cleared the threshold for relevance and admissibility, but in my view its probative value is extremely weak.  Prejean is known to be a vigorous advocate for one side of this debate, and her assessment of the sincerity of Tsarnaev's remorse isn't worth a wooden nickel, IMHO.

Bill notes that the jury is likely to question why Tsarnaev did not take the stand and express that remorse himself.  Undoubtedly.  But can the prosecutor argue that in his closing argument?  Surprisingly, that question remains undecided.

Justice Scalia's dissenting opinion in Mitchell v. United States, 526 U.S. 314 (1999) (joined by Chief Justice Rehnquist and Justices O'Connor and Thomas) gives a bit of the background:

Despite the text [of the Fifth Amendment], we held in Griffin v. California, 380 U.S. 609, 614 (1965), that it was impermissible for the prosecutor or judge to comment on a defendant's refusal to testify. We called it a "penalty" imposed on the defendant's exercise of the privilege. Ibid.

*                                    *                                      *

The Court's decision in Griffin, however, did not even pretend to be rooted in a historical understanding of the Fifth Amendment. Rather, in a breathtaking act of sorcery it simply transformed legislative policy into constitutional command .... To my mind, Griffin was a wrong turn which is not cause enough to overrule it, but is cause enough to resist its extension.

The majority in Mitchell did extend the rule a bit.  ""We decline to adopt an exception [to Griffin] for the sentencing phase of a criminal case with regard to factual determinations respecting the circumstances and details of the crime." Id., at 328 (emphasis added).  Notice how carefully limited that rule is.  Mitchell did not make a blanket holding that Griffin applies completely to the penalty phase.  What about remorse?

"Whether silence bears upon the determination of a lack of remorse ... is a separate question. It is not before us, and we express no view on it." Id., at 330 (emphasis added).

That question remains unanswered by the high court.  In the case of Kentucky murderer Robert Keith Woodall, the Kentucky Supreme Court held that there was no requirement to give the jury a "no adverse influence" instruction and found Mitchell distinguishable.  See Woodall v. Commonwealth, 63 S.W.3d 104 (2001).  The Sixth Circuit disagreed and granted federal habeas corpus relief.  CJLF's brief in the case is here.

The Supreme Court rebuked the Sixth for substituting its own opinion for that of the state supreme court on an unsettled question.  "In so doing, it disregarded the limitations of 28 U. S. C. §2254(d)--a provision of law that some federal judges find too confining, but that all federal judges must obey. We reverse."

On the underlying question:  "We need not decide here, and express no view on, whether the conclusion that a no-adverse-inference instruction was required would be correct in a case not reviewed through the lens of §2254(d)(1)."  That also goes for the no-comment rule, of which the no-adverse-inference instruction rule is a corollary.  "Indeed, Mitchell itself leaves open the possibility that some inferences might permissibly be drawn from a defendant's penalty-phase silence."

I doubt the prosecutor actually will hammer on this point.  It's not worth risking reversal.  Let some other case be the "test case."

The other issue is slipping in the bit about the Catholic Church.  Invoking religious authority before the jury is highly improper, regardless of who does it, and I do not doubt she knew it was improper when she did it.  An objection and an instruction to the jury does not really cure anything, and everyone knows it.  That should be sufficient to get her barred as a witness in future trials.

Update:  Denise Lavoie has this story for AP:

Prosecutors had fought unsuccessfully to keep Prejean off the witness stand.

During cross-examination by prosecutor William Weinreb, Prejean acknowledged she's considered one of the leading death penalty opponents in the country and believes no one deserves to be executed, no matter what the crime.

Liz Norden, the mother of brothers J.P. and Paul Norden, who each lost a leg in the bombings, was unmoved by what Prejean had to say about Tsarnaev.

"If he was that remorseful, then he should have gotten up on the stand and said how sorry he is," Norden said. "To have other people get up and talk on his behalf, it means nothing to me."

Tsarnaev was convicted of all 30 charges against him, including 17 that carry the possibility of the death penalty. He did not take the stand during either phase of the case.

The 12-member jury must be unanimous for him to get the death penalty. If even one juror votes against execution, he will be sentenced to life in prison.