TASTE COMMENTARY

That's the storyline: Gullible juries, fooled by television into believing their local crime labs are more shrewd and definitive than they actually are, are handing down "not guilty" verdicts unless prosecutors come up with fancy forensic evidence. From Baltimore to Peoria prosecutors complain that one of the most popular TV shows in America is preventing jurors from doing the right thing. Joshua Marquis, the director of the National District Attorney's Association, says: "We're hearing stories where people, jurors will come back and say: 'There was no DNA test. I expected that. And without that I'm not convinced.'"

Could this be true? Could a TV show--OK, three TV shows if we count the spin-offs, not to mention other forensic-themed series like "Crossing Jordan"--actually change the disposition of criminal cases in the U.S.?

hat television might have an effect on courtrooms is not implausible. As Anthony Amsterdam and Jerome Bruner note in "Minding the Law" (2000), "judges and lawyers must inevitably rely upon culturally shaped processes of categorizing, storytelling, and persuasion in going about their business." TV has become our principal storyteller, transmitting legal norms or, arguably, creating them. It's been said that "NYPD Blue," like cop shows before it, educated the public about its Miranda rights. Other scholars talk about a "Perry Mason effect," which may cause juries to expect on-the-stand confessions like the ones Raymond Burr elicited week after week.

But to argue that "C.S.I." and similar shows are actually raising the number of acquittals is a staggering claim, and the remarkable thing is that, speaking forensically, there is not a shred of evidence to back it up. There is a robust field of research on jury decision-making but no study finding any "C.S.I. effect."

There is only anecdotal evidence. In the media storm, prosecutors have pointed to cases (roughly 20 by our count) in which, they believe, juries acquitted because of unreasonable expectations for forensic evidence. But that is a thin reed on which to rest such a broad claim. We don't even know whether the overall rate of acquittals has gone up or down. For all we know, the jurors in such cases have felt genuine reasonable doubt, not a "C.S.I." version of it.

Laurie Levenson, a professor at Loyola Law School in Los Angeles, calls the Blake verdict, for example, "a reasonable-doubt case." If Mr. Black got off when he shouldn't have, other explanations easily come to mind: The defense team, for instance--blessed with staggering resources compared with those of most defendants--may have done an especially good job on behalf of its client.

It is not even quite clear what the "C.S.I. effect" actually is. Prosecutors claim that the show makes juries less inclined to convict because they have inflated expectations for the comprehensiveness, sophistication and clarity of forensic evidence--all those threads and fibers and DNA traces left behind at crime scenes. But the effect could work the other way, too.

Defense attorneys contend that the show makes juries inclined to convict because it portrays forensic evidence as unambiguous and more certain than it is. Lisa Steele, the co-chair of the Forensic Evidence Committee for the National Association of Criminal Defense Lawyers, suggests that "C.S.I." is "making folks less skeptical about the potential for forensic error or fraud." Max Houck, the director of the Forensic Science Initiative at West Virginia University, argues that the show "incorrectly depicts forensic science as this juggernaut of infallibility."

Media coverage gives another version of the "C.S.I. effect," too: that the show is attracting record numbers of college students into forensic-science programs, much as "E.R." drew them into medicine, "L.A. Law" into law and "All the President's Men" into journalism. Perhaps so. But in that case the true "C.S.I. effect" is the absurdly glamorous image of crime-scene investigators as good-looking, hard-bodied and deeply involved, day after day, in fascinating, rewarding work. No one should choose an occupation based on Hollywood's version of it.

"C.S.I." creator Anthony Zuiker suggests yet another effect: that the show is educational. "People know science now," he says. "They watch 'C.S.I.'" But experts agree that much of the forensic science depicted on "C.S.I."--40%, according to forensic scientist Thomas Mauriello--does not even exist. And even when the techniques are real, the neatly perfect depictions of collecting, processing and analyzing evidence are not.

Just how this idealized image might affect juries is not clear. Ms. Steele complains that the defendant's version of the "C.S.I. effect" "hasn't been getting any traction in the media." Judging by recent stories, she is right. Most coverage, especially on TV, has discussed only one effect: inflated jury expectations crippling prosecutors. But the coverage is over-the-top and weakly sourced whatever its angle.

The real "C.S.I. effect" may turn out to be caused not by "C.S.I." but by the media's coverage of it. Could it be that the most dramatic search for evidence should begin in a newsroom? It would make a great show.
Mr. Cole is an assistant professor of criminology, law and society at the University of California, Irvine. Ms. Dioso is a graduate student there.