In both civil and criminal trials, the legal system depends on expert witnesses to assist the judge and the jury in understanding and ruling reasonably on what may be complex technical or scientific issues. In courtrooms across the country, expert witnesses offer opinions on virtually any subject.
As a result, with experts on both sides often offering opinions that are directly at odds with each other, it's hardly unusual for cases to come down to a "battle of the experts" in which the jury decides which expert is more credible or reliable.
The pressure to convince jurors has led to at least some expert testimony that has little basis in scientific fact—what author Peter Huber coined "junk science" in his influential 1991 book "Galileo's Revenge: Junk Science in the Courtroom."
In an effort to guard against junk science making it into the courtroom, the U.S. Supreme Court concluded in the 1993 case of
Courts have to consider factors like whether the scientific theory or evidence has been tested; published or otherwise reviewed by peers; what its error rate is; and whether or not such a theory has been generally accepted in the scientific community. Both sides have an opportunity to challenge the opposition's expert testimony in a hearing held before any such evidence comes before a jury.
Although holding such "Daubert hearings" have helped keep junk science out of the courtroom, that doesn't mean that self-styled experts on unusual subjects don't crop up.
In 22 years of trying cases, I've seen a witness who professed to be an expert on walking (I asked him how many miles he had to walk to qualify as an "expert"), a cultural anthropologist prepared to testify about African-American wedding traditions like "jumping the broom," and even a confessed "witch doctor" who wanted to testify about her "alternative healing" of a personal injury plaintiff.
Criminal cases seem to bring out some of the strangest subjects for expert testimony and recreations in the name of getting at the truth.
In the high profile Casey Anthony murder trial, for example, testimony about whether or not Caylee Anthony's body had been in a car trunk led to testimony from an expert on the smell of decomposing bodies (I really don't care to know how one becomes an expert in that field).
The 2008 trial of China Arnold of Ohio, who was charged with aggravated murder when her 3½-week-old daughter died after being placed in a microwave oven, also involved grisly expert testimony. A prosecution expert tried to simulate the injuries the body suffered using calf brains, chicken torsos and a doll similar in size to the infant. Not to be outdone, the defense called an expert pathologist in rebuttal, to point out the lack of reliable studies on what can happen to children in microwaves.
Sometimes, the battle of experts is a bit of a mismatch. Trace Rae and Jennifer Toms of Wasilla, Alaska, were each facing multiple drug charges in federal court, primarily for cultivating marijuana.
The charges were supported by the expert testimony of a supposed olfactory "Rainman," Alaska State Trooper Kyle Young, who claimed that he was able to smell the odor of marijuana while 450 feet away from an enclosed building.
Trooper Young, who has more than 20 years of experience and has seized between 100 to 150 marijuana-growing operations since 1998, said that he "located by smell," using his "the nose knows" approach to get a search warrant. A search of the premises revealed 500 marijuana plants. But was his search justified—could he have actually smelled the marijuana under those circumstances?
Not according to the defense's expert witness, David Doty. Doty is the director of the Smell and Taste Center at the University of Pennsylvania School of Medicine. He pointed out that Young was inside his vehicle, parked at least 450 feet away from the building in question—which had no windows, two insulated and sealed doors, and was equipped with a large charcoal air filter designed to capture odor.
For Trooper Young to have smelled what he claimed to smell, a perfect storm would have had to occur: a nonfunctional air filter and air currents that carried the pot smell up and over vegetation as well as around a house and then down to a police vehicle 450 feet away.
Doty opined that there was "zero probability" that Young could have smelled the marijuana that he claimed. U.S. District Judge John Sedwick agreed, and threw out the seized evidence, gutting the prosecutor's case.
Some expert testimony can be dubious even without a "smell test." The gentleman's club Nite Moves of Latham, N.Y., contested an audit by New York state tax authorities who ruled that the establishment owed roughly $125,000 in sales tax on private lap dances. The club appealed to the New York Supreme Court Appellate Division, claiming that the lap dances were "dramatic or musical art performance," and thus tax exempt under New York law.
The strip club even offered an expert witness — a cultural anthropologist "who has conducted extensive research in the field of exotic dance," and who testified that the lap dances (or "presentations," as she preferred to call them) were "unequivocally live dramatic choreographic performances."
However, the court ruled that Nite Move's evidence was insufficient, in part because their expert was offering opinions on "private dances" that, as it turns out, she didn't actually witness (hey, they are private, after all). Consequently, Nite Moves was stuck with the tax bill.
Nite Moves still has a few legal moves of its own; its lawyer, Andrew McCullough, says the club plans to appeal the decision to a higher court. Barring that, they could pay the tax bill — even if they did so with 125,000 sweaty, crumpled-up singles.
Finally, there's the question of whether the subject is one that even requires specialized knowledge or experience beyond that of ordinary people. The Iowa Court of Appeals recently confronted this issue when prison inmate Steven Landis appealed his conviction for assaulting a guard with bodily fluid—that is, Landis' own feces.
Landis argued that while there was testimony about the brown liquid and its foul stench, the state didn't prove its case since there was no expert testimony confirming that it was actually feces. The appellate court disagreed, saying that was unnecessary.
Paraphrasing the old adage, the court held that "If it looks like feces, if it smells like feces, if it has the color and texture of feces, then it must be feces. No witness with a degree in scatology was required, nor was scientific testing required to establish the fact the substance was feces."
As for the rest of Landis' arguments, the court felt that they were full of — well, a certain brown substance that rhymes with "grit."