Marie Gryphon has this piece in the National Law Journal refuting the common misconceptions that "criminal defendants can't get a break from conservative judges" or that "Republican appointees decide criminal cases based on the identity of the parties rather than the content of the law."  Gryphon writes that in criminal cases involving statutory interpretation, "strict constructionist" justices such Scalia and Roberts take the same restrained approach they do in cases involving constitutional interpretation.  In the statutory cases, this approach often favors the criminal defendant, whose conduct may not be criminal under a narrow reading of the law.  In fact, Gryphon argues,

"In the nine criminal cases the Court decided last term that raised questions of statutory rather than constitutional interpretation, Justice Antonin Scalia, Chief Justice John Roberts Jr. and Justice Anthony Kennedy were among the most 'liberal' on the Court: They sided with the criminal defendants in these cases eight out of nine times.  The only justice with a more pro-defendant record on these cases last term was John Paul Stevens."

See also Kent's post here on this subject.