The Supreme Court ruled unanimously yesterday that federal judges must decide if novel "expert" testimony is reliable enough to be heard at trial.
The 9-0 decision expanded the court's 1993 ruling banishing "junk science" to cover all experts in federal courts and requiring their evidence to be within the bounds of professional acceptance, not radical or unproven speculation reserved for courtroom use.
"It is to make certain that an expert - whether basing testimony upon professional studies or personal experience - employs in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field," Justice Stephen G. Breyer wrote for the court.
Justice Breyer told judges how to decide when to allow a perfume tester "to distinguish among 140 odors at a sniff" or an art expert to identify magenta. But he said peer acceptance is meaningless in a discipline that "lacks reliability," such as astrology or seances seeking guidance from the dead.
Justice John Paul Stevens dissented from a separate 8-1 vote to throw out expert witness Dennis Carlson Jr.'s testimony about what caused a tire to blow, overturning Patrick Carmichael's van and killing a child in the 1993 Alabama accident.
Legal analysts call the decision an enormous boon to manufacturers plagued by product-liability lawsuits based on novel cause-and-effect theories.
"Jury verdicts are a perfect example of regulation by tort lawsuit," said Mobile, Ala., lawyer Joseph P.H. Babington who defended Kumho Tire Co., which made the Hercules-brand tire that virtually disintegrated.
"You can get an expert to say just about anything. Both sides can do it, but as a practical matter plaintiffs have the burden of proof, so they're the ones who wind up hiring the fly-by-night expert," Mr. Babington said.
"If you're going to regulate products through lawsuits, you should be certain that a court verdict is sound and not based on junk science or some cockamamie theory from a bought-and-paid-for expert," he said, paraphrasing Justice Antonin Scalia's question at the Dec. 7 oral argument.
Justice Scalia put it more elegantly yesterday, calling the ruling a reasonable way to exclude "expertise that is fausse [French for twisted or warped] and science that is junky. …