Crime laboratory reports may not be used against criminal defendants at trial unless the analysts responsible for creating them give testimony and subject themselves to cross-examination, the Supreme Court ruled Thursday in a 5-to-4 decision.

The ruling was an extension of a 2004 decision that breathed new life into the Sixth Amendment’s confrontation clause, which gives a criminal defendant the right “to be confronted with the witnesses against him.”

Four dissenting justices said that scientific evidence should be treated differently than, say, statements from witnesses to a crime. They warned that the decision would subject the nation’s criminal justice system to “a crushing burden” and that it means “guilty defendants will go free, on the most technical grounds.”

The two sides differed sharply about the practical consequences of requiring testimony from crime laboratory analysts. Justice Anthony M. Kennedy, writing for the four dissenters, said Philadelphia’s 18 drug analysts will now each be required to testify in more than 69 trials next year, and Cleveland’s six drug analysts in 117 trials each.