Just how distinct is the smell of death, and what role does perception play in identifying it? That depends on whether you're a young woman fighting for your life or a prosecutor seeking a conviction. Despite the courtroom's emphasis on backing claims with science, attorneys fail to consider the contribution of cognitive science. The uncertainty surrounding novel techniques tends to showcase it.

In 2011, Casey Anthony went on trial as an accused murderess. The badly decomposed remains of her two-year-old child, Caylee Marie, had turned up in a bag in the woods. The prosecutor believed the remains had been stored for a brief time in the trunk of her car, which emitted a foul smell. The defense said the odor was from trash. Both sides clashed over an odor identification method, with claims of "junk science" and "fantasy forensics" flung like rotten tomatoes.

The Casey Anthony trial is done (she was acquitted), but forensic scientists still debate certain controversial items. Although the prestigious American Academy of Forensic Sciences devoted its annual conference last week to "Global Research," the 4,000-plus attendees might have had the impression that it was really about Casey Anthony.  

A full-day workshop, a packed plenary session, a breakfast presentation, and a luncheon all featured some aspect of the case, not to mention numerous heated debates each evening in the hotel bar. Prosecutor Jeff Ashton was on hand to talk about his strategy, while defense attorney Jose Baez (who just parted ways with his infamous client) joined his defense team's analysis. Both sides focused on the use of novel evidence, with each supporting the merits of a specific approach.

That's the thing about novel evidence. Depending on how it serves your purpose, you can offer it as a potential scientific breakthrough or you can claim it's untested and therefore inadmissible. After all, DNA analysis had a first time in court, and it, too, had to survive challenges. On the other hand, some novel techniques that seemed viable have been discredited.

One of the most intriguing debates in the Anthony case concerned "decomposition odor analysis," or DOA. For the prosecution, Dr. Arpad Vass gave a rundown. As a research scientist at Oak Ridge National Laboratory, he'd worked for two decades on microbial measurements from decomposition, amassing a database of over 400 compounds from body vapors. He stated that his method could distinguish between living and dead odors, human and animal. When he tested a canister that captured air from the trunk of Anthony's car, he concluded that it contained human decomposition odor.

Baez tried to prevent this evidence from being admitted. It was untested and not yet peer-reviewed. It should not be allowed to influence decisions about a person's life. He attacked Vass as a scientist and used his own experts to show the flaws.

So, who's right? Despite a series of intense presentations to the world's experts, the standoff persists. Those who wish to use the "sniff test" in the future will have to work harder to establish it as a science. Those who wish to oppose it will have to watch for weakness in these efforts. During the process, both sides will be influenced to some degree by what they hope for and what they need.

Despite the scientific context for these debates, no one addressed the cognitive factors involved. "Facts" are sifted through our cognitive maps, proven by centuries of scientists changing their collective minds on key interpretations. To even perceive something as a potential fact, we first imbue it with meaning that derives from a mix of circumstances, experience, need, emotion, and mental set. We generally don't notice how this all mixes together to give the fact substance, but if it meets our needs, the result feels "right."

Thus, subjective factors can subtly shift facts to work for our agendas. Testing and analysis can then solidify or undermine them. Reality isn't up for grabs, of course, but some things are not what they first had seemed.

I listened to some of the heated debates at the AAFS meetings about "odor mortis." No matter how many professionals weighed in, the issue was not settled. But one thing was clear: need and emotion will continue to fuel both sides until repeated validation (or lack of it) subtracts the uncertainty that allows psychological factors room to play.

I had no stake in the outcome, but it was interesting to watch those who did. We kid ourselves if we think facts and mental sets are unrelated.


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