WASHINGTON — The Supreme Court on Thursday buttressed a criminal defendant’s right to cross-examine prosecution witnesses, ruling in favor of a New York man who was convicted of killing a 2-year-old boy on Easter Sunday in 2006.By an 8-1 vote, the justices held that defendant Darrell Hemphill’s constitutional rights were violated when a judge allowed jurors to read another man’s testimony that prosecutors used to undermine Hemphill’s defense. The man, Nicholas Morris, was unavailable at the trial.Hemphill argued that …