The fascination many Americans have with criminal investigation can be summarized in three letters: CSI. The original series on crime scene investigation was so successful that it has spawned series-after-series of sequels.

Real-life lab work, however, is not always as glamorous - or as accurate - as it is sometimes depicted on the television screen. And yet the work done in those labs is often crucial in St. Louis criminal defense cases, as well as cases across the country.

Unfortunately, the labs don't always get it right. Sometimes they botch routine tests and fail to follow established scientific protocols.

There is also the related issue of how evidence from crime laboratories is to be introduced at trial, where constitutional protections grant defendants the right to confront their accusers.

Last year, in a case called United States v. Williams, the U.S. Supreme Court faced the issue of whether a forensic analyst could properly testify about a DNA profile that had been performed by someone else. The case involved a rape trial in which the prosecution sought to show that DNA taken from inside the victim was a match for a DNA sample from the defendant.

Legally, the case turned out to be quite complicated. There was no majority opinion among the nine justices. But the reasoning in the case limits the ability of the prosecution to introduce testimonial statements thorough expert witnesses who are not forensic experts.

In practice, then, the Confrontation Clause of the Sixth Amendment continues to serve as a check on introducing formal forensic reports at trial without testimony from the person who produced the reports. There are many types of forensic tests this should refer to besides DNA. It could include tests of:

• Blood alcohol

• Drugs

• Fingerprints

It could also include autopsy reports. In short, reports that are based by tests conducted by one person and, unless rebutted, are incriminating still require the testimony of the tester to be admissible.

Source: "The holdings and implications of Williams v. Illinois," SCOTUSblog.com, Jeffery Fisher, 6-20-12