Justice Thomas spoke for a 5-4 majority, reversing a decision of the 9th circuit sitting en banc. Here is the highlight:
Even assuming the truth of all the facts Landrigan sought to prove at the
evidentiary hearing, he still could not be granted federal habeas relief because
the state courts' factual determination that Landrigan would not have allowed
counsel to present any mitigating evidence at sentencing is not an unreasonable
determination of the facts under 2254(d)(2) and the mitigating evidence he seeks
to introduce would not have changed the result. In such circumstances, a
District Court has discretion to deny an evidentiary hearing.