In the case of Shawn Patrick Lynch v. Arizona in 2015, the U.S Supreme Court ruled against Lynch who was convicted for first-degree murder and sentenced to death by an Arizona court. The main issue at hand was whether or not the trial judge had erred in instructing jurors that they could consider mitigating evidence (evidence which might lessen a defendant's culpability) only if it bore a causal nexus to the crime committed. In other words, could this evidence be considered only if it directly related to why he committed his crime? The defense argued that such instruction limited their ability to present all relevant mitigating evidence as required under Eddings v Oklahoma (1982). However, both state courts and federal appeals courts upheld Lynch’s conviction and sentence on grounds that any error made by trial judge did not have substantial influence on jury verdicts. When appealed further, Justice Clarence Thomas denied certiorari stating there were no grounds for review since lower courts' decisions were consistent with previous rulings from Supreme Court itself.

In the dissenting opinion for Shawn Patrick Lynch v. Arizona, Justice Stephen Breyer argued that the jury was not properly informed about a critical aspect of sentencing. He believed that jurors should have been told explicitly that if they did not unanimously agree on death penalty, then Lynch would be sentenced to life imprisonment without parole. Instead, the judge instructed them only to consider whether there were mitigating circumstances sufficient enough to call for leniency but didn't mention what would happen if they couldn't reach an agreement on this matter. According to Breyer and two other justices who joined his dissent (Justices Ginsburg and Sotomayor), this omission could have led some jurors to vote for death sentence out of fear that failing unanimity might allow Lynch's release someday - which wasn't true as per state law.