Alito's first opinion on the Court ruled that it was unconstitutional for a criminal defendant's evidence of third-party guilt to be excluded based only on the strength of the prosecution's case. This standard was irrational because whether the prosecution's evidence was strong had no logical bearing on the reliability and probative value of the defendant's proffered evidence.
Alito's unanimous decision ruled that a criminal defendant cannot prospectively waive the protections of the Speedy Trial Act of 1974. Justice Scalia declined to join the portion of Alito's opinion addressing the Act's legislative history, and wrote a separate concurrence criticizing that method of statutory interpretation.
Alito concurred in the Court's opinion and in its 7-2 judgment that a defendant charged with the federal crime of receiving a firearm while under indictment had the burden of proving the affirmative defense of duress. Alito wrote separately to express his understanding that the allocation of the burden would not vary from one federal criminal statute to another. The defendant had the burden at common law, and Alito did not believe Congress reassessed the burden with every new statutory enactment so that the allocation would impliedly follow the current legal trends.
Alito's majority opinion ruled that the Prison Litigation Reform Act required administrative remedies to be properly exhausted before prison conditions could be challenged in federal court. Remedies that were unavailable only because they were time-barred were not properly exhausted.
Alito's first dissent on the Court argued that the Court had misinterpreted the Sixth Amendment's protection of the right to counsel to protect a defendant's choice of counsel, when he believed the text and history of the Amendment indicated that it merely protected a defendant's right to assistance that was as effective as his choice of counsel would be. Even if it protected choice of counsel, it did not mean that violation of this right should be grounds for automatic reversal. Instead, because the Constitution lacked directives as to how such rights should be enforced, the Court should follow the Congressional directive to apply harmless error analysis.
Alito wrote the five-justice majority for a 6–3 decision that prevailing parents under the Individuals with Disabilities Education Act were not entitled to an award of expert witness fees. Justices Souter and Breyer filed dissenting opinions.
