But a Supreme Court decision has sent a jolt through that procedure.
Now the prosecution must make a lab technician available to testify in person if the defendant demands it. As a result, some cases already have been dismissed. One state, Virginia, has called a special legislative session to change its laws. And some lawyers think the ruling will continue to have a major effect.
In a 5-4 decision, the high court said that lab reports served as “witnesses” for the prosecution. And because the 6th Amendment gives defendants a right to "be confronted with the witnesses against him," Justice Antonin Scalia said that drug defendants and others were "entitled to be confronted with the [lab] analysts at trial."
While Scalia said the decision upheld the basic right to question the prosecution's witnesses, the four dissenters said the ruling had "vast potential to disrupt" the criminal courts. They also said it gave "a great windfall" to defendants, some of whom could have their cases dismissed because a lab technician was not available to testify.
Some prosecutors have said they fear the uncertainty -- and the potential cost -- of being required to have lab technicians ready to testify.
"This is a train wreck in the making," said Scott Burns, executive director of the National District Attorneys Assn. "The court is saying you can't submit an affidavit saying that the cocaine is cocaine. The criminalist must be there to testify the cocaine is cocaine. Particularly in rural states and in smaller communities, this is going to be a major problem."