The district court did not abuse its discretion in refusing to ask prospective jurors what facts they had learned from the media in the Boston Marathon bombing case, the U.S. Supreme Court held March 4 in United States v. Tsarnaev
Nor did the district court abuse its discretion in the penalty phase by excluding hearsay evidence that the defendant-Tsarnaev’s brother had committed a prior murder, which Tsarnaev sought to introduce as mitigation to show he was under his brother’s domination, the Court held.
Dzhokhar Tsarnaev and his older brother, Tamerlan, planted and detonated two home-made bombs at the Boston Marathon in 2013, killing three people.
Tamerlan was killed three days later, when Dzhokar inadvertently ran over him as police pursued them.
Dzhokar Tsarnaev was charged with capital crimes. 
Prior to trial, the district court presented prospective jurors with a 100-question form proposed by the parties, but the court rejected one media-related question asking prospective jurors to list facts they had learned about the case from the media.  The court refused to allow defense counsel to ask a similar general question at voir dire.
Instead, the court allowed counsel to ask follow up questions based on prospective juror’s answers.  Several times, the court allowed Tsarnaev’s attorneys to follow up on a prosepective juror’s earlier answer with specific questions about what the juror had seen or heard in the news.
Tsarnaev did not contest his guilt at trial, but during penalty phase, centered his mitigation on the idea that he had been under the domination of his brother, Tamerlan.  Tsarnaev contended he was not sufficiently culpable to warrant the death penalty because his brother had pressured him to participate.
To support Tamerlan’s domineering nature, Tsarnaev sought to introduce hearsay evidence that Tamerlan had committed a prior triple murder in Waltham, Mass., in 2011.  
Shortly after the Marathon bombing, FBI agents interviewed a friend of Tamerlan, who told agents that he and Tamerlan had participated in a robbery in Waltham in 2011, during which Tamerlan had killed three people.  When agents asked the friend to write out his confession, the friend instead attacked the agents, who killed him in self-defense.
The Government successfully sought a motion in limine to exclude the Waltham-murders evidence on grounds it was lacking in probative value and would be confusing to jurors.
The district court agreed.  The court found the evidence did not show what Tamerlan’s role was, and with the friend dead, there was no further line of inquiry to pursue.
Tsarnaev was convicted of 30 federal crimes, and sentenced to death for six of them.
The First Circuit reversed.  It ruled the district court erred in refusing the general voir dire question about media coverage, and in excluding the Waltham-murders evidence as mitigation.
Voir dire inquiry rejected 
The Supreme Court reversed, in a 6-3 opinion. 
Trial judges are primarily responsible for evaluating the impact of pretrial publicity since “the judge sits in the locale where the publicity is said to have had its effect”, and the judge “may base her evaluation on her own perceptions of the depth and extent of news stories”, the Court said.
“Because conducting voir dire is committed to the district court’s sound discretion, there is no blanket constitutional requirement it must ask each prospective juror what he heard, read, or saw about a case in the media”, the Court said.  “Instead, as in any case, the district court’s duty is to conduct a thorough jury-selection process that allows the judge to evaluate whether each prospective juror is to be believed when he says he has not formed an opinion about the case.”
Here, the court submitted a 100-question form to prospective jurors which asked them what media sources they followed; how much media they consumed; whether they had previously commented on the bombings; and whether they had formed opinions on guilt or innocence.  
The court also subjected prospective jurors to three-weeks of individualized voir dire in which both parties were able to probe for bias.  Tsarnaev’s attorneys were permitted to ask several jurors what they heard, read, or had seen about the case.
 “In sum, the court’s jury selection process was both imminently reasonable and wholly consistent with this Court’s precedents,” the Court said.
The First Circuit justified its reversal as an exercise of its “supervisory authority” to establish rules for voir dire in high-profile cases.  But “lower courts cannot create prophylactic supervisory rules that circumvent or supplement legal standards set out in decisions of this Court,” the Supreme Court said.
“Whatever the ‘supervisory power’ entails, it does not countenance the Court of Appeals’ use of it,” the Court said.
Mitigating evidence rejected
Under the Federal Death Penalty Act, a district court may exclude evidence if its probative value is outweighed by the danger of unfair prejudice, confusing the issues, or misleading the jury.
Tsarnaev contends that exclusion the Waltham-murders evidence violated the Eighth Amendment, because the jury must be required to consider all mitigating circumstances.
But “because States and the Federal Government retain the traditional authority to decide if certain types of evidence may have insufficient probative value to justify their admission, they may enact reasonable rules governing whether specific pieces of evidence are admissible,” the Court said.
Statutes or rulings which categorically exclude certain types of mitigating evidence violate the Eighth Amendment.  But the Federal Death Penalty Act’s balancing test “does not put any category of mitigating evidence beyond the sentencer’s purview”, the Court said.  Instead, the statute “preserves the traditional gatekeeping function of district court judges to consider and assess specific pieces of relevant evidence in light of its probative value and the risks it poses to the jury’s truth-seeking function.”
The Court agreed with the district court that the Waltham-murders evidence did not show whether Tamerlan or the friend was the leader of those murders.  “And it certainly did not show that … Tamerlan led and dominated Dzhokhar in a manner that would mitigate Dzhokar’s guilt” in the Marathon bombings, the Court said.
The Waltham-murders evidence “risked producing a confusing mini-trial where the only witnesses who knew the truth were dead,” the Court concluded.  “The District Court did not abuse its discretion by declining to lead the jury into this evidentiary detour.”
Other opinions
Justice Barrett, joined by Justice Gorsuch, wrote separately to note her “skepticism” that the Courts of Appeals possess “supervisory authority” over district  courts at all.
Article III gives courts inherent authority to regulate their “own proceedings”, Barret said.  “But here, the First Circuit did not adopt a rule regulating its own proceedings – it adopted a blanket rule that all district courts in its jurisdiction must follow on pain of reversal.”
Barrett said Tsarnaev’s case does not require the Court to determine whether Courts of Appeals have “supervisory authority” over district courts, but the Supreme Court should revisit that issue in the future.
Justices Breyer, Sotomayor and Kagan dissented.