Lab experts can be called as witnesses


The Supreme Court announced Thursday a potentially significant change in how crime lab reports are used in trials, ruling that a defendant has the right to cross-examine in front of the jury the experts who prepared these reports.

Crime labs have been subjected to criticism in the last decade, much of it because of DNA evidence that has shown at least 240 prisoners were in fact not guilty. In many instances, they were convicted based on faulty tests involving hair samples, clothing fibers, blood or ballistics from guns.

Often, these crime lab reports were simply introduced as evidence. They were assumed to be accurate.


In Thursday’s opinion, Justice Antonin Scalia said technicians who prepared these reports acted as “witnesses” for the prosecution. And under the 6th Amendment, the accused has the right “to be confronted with the witnesses against him.”

Scalia wrote for a 5-4 majority that reversed the conviction of a Massachusetts man found guilty of selling cocaine.

Police officers took 19 small bags from a car in which Luis Melendez-Diaz was riding. At the trial, the prosecution submitted a certificate from a state lab that said the bags contained cocaine. Melendez-Diaz objected, and his lawyer said he wanted to challenge the evidence. But the objection was overruled, and the defendant found guilty.

In Melendez-Diaz vs. Massachusetts, the high court reversed his conviction on the grounds that his right to confront his accuser had been violated.

Scalia said states can work out procedures that require defendants to notify prosecutors and lab technicians in advance if they wish to question them in court. “The sky will not fall after today’s decision,” he said, rebutting sharp criticism from the four dissenters.

Stanford law professor Jeffrey Fisher, who represented the defendant, said the ruling has national significance. “It means the prosecution must be ready to present forensic evidence through live testimony if the defendant requests it,” he said.


The court lineup was unusual. Scalia was joined by Justices John Paul Stevens, David H. Souter, Clarence Thomas and Ruth Bader Ginsburg.

The dissenters, led by Justice Anthony M. Kennedy, said the ruling “has vast potential to disrupt criminal procedures that already give ample protections against the misuse of scientific evidence.”

He said the ruling could mean that others who gathered or prepared lab samples might be called to testify. And he worried that cases could be thrown out if these experts were unavailable, even if they had died in the interim.

Kennedy insisted “laboratory analysts who conduct routine scientific tests are not the kind of conventional witnesses” who are referred to in the 6th Amendment. Chief Justice John G. Roberts and Justices Stephen G. Breyer and Samuel A. Alito Jr. also dissented.