The reliability of crime labs has been questioned in several states and at the federal level in recent years.

State and federal courts have come to different conclusions about whether recent Supreme Court decisions affirming the constitutional right of a defendant to confront his accusers extend to lab reports that are used in many drug and other cases.

The case the justices accepted, and will consider in the fall, comes from Massachusetts. Luis Melendez-Diaz was convicted of trafficking in cocaine partly on the basis of a crime lab analysis that confirmed that cocaine was in plastic bags found in the car in which Melendez-Diaz was riding.

Rather than accept the report, however, Melendez-Diaz objected that he should be allowed to question the person who prepared it about testing methods, how the evidence was preserved and a host of other issues.