Bruton and non-testifying codefendant's statements inculpating other defendant
In a lengthy Fourth Circuit Court of Appeals case (United States v. Benson, No. 18-4539, 2020 WL 1966843 (4th Cir. Apr. 24, 2020)), the court examined the issues of hearsay, Confrontation Clause, and Bruton. In this case, the government tried multiple defendants at the same time. There were multiple statements made by the defendants that were introduced throughout the trial either under 'admission by party opponent' (FRE 801) or 'statement against interest' (FRE 804). The defense challenged that these statements were testimonial and inculpatory, and thus violated Bruton.
Bruton
When multiple defendants are tried at the same time, an issue that often arises is statements that other defendants made. If Defendant A gave a statement to the police, then typically during his trial, anything A said can be used against him as nonhearsay (FRE 801).
But an issue arises when Defendant A and B are on trial together, and A told the police that B committed the crime. Everything A says is generally nonhearsay (admission party opponent), and A has a constitutional right to remain silent and not take the stand; so how does B get to exercise his right to confront A and cross examine him on his statement? That's where Bruton comes into play:

United States v. Benson, No. 18-4539, 2020 WL 1966843, at *4 (4th Cir. Apr. 24, 2020)
So Bruton "held that a defendant is deprived of his Sixth Amendment right of confrontation when the facially incriminating testimonial statement of a non-testifying codefendant is introduced at their joint trial, even if the jury is instructed to consider the confession only against the codefendant" Id. at *5 (4th Cir. Apr. 24, 2020)(emphasis added)
Testimonial
So in order for Defendant A's statement to be excluded (under Bruton), it has to be facially incriminating and testimonial. What is testimonial:

Conversations among friends:

(“Bruton is simply irrelevant in the context of nontestimonial statements.”);
“testimonial evidence does not include statements made to friends in an informal setting,” Id. *6 (4th Cir. Apr. 24, 2020)
Statements to cell mates:

"concluding that statements to a cellmate are plainly nontestimonial and thus do not implicate Bruton" Id. at *5 (4th Cir. Apr. 24, 2020)
Facially Incriminating
The testimonial statement also has to be "facially incriminating"

Inference and possibility of implication:

Other circuits interpretation:

Conclusion
The court held that none of the challenged statements were "testimonial" and/or "incriminating" and thus Bruton was not triggered. However, the government still had to introduce them through the Federal Rules of Evidence. The court concluded (with a harmless error standard), that most of the statements would either fall under admission by party opponent (801) or statement against interest (804).
Judge Richardson concurred in part because he disagreed that one statement made to an investigator was incriminating and thus triggered Bruton. Additionally another statement was not properly analyzed under 801. However, he would've still held these as harmless error and concurred with the majority's result.
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