Currently, victims of violent crimes must use visual memories to identify the criminal (known as the eyewitness lineup), but studies have shown that eyewitnesses actually show a decreased accuracy in recognizing culprits visually, perhaps due to the trauma associated with the event. If there was another way that humans could identify perpetrators of crimes — relying on a deeply intuitive sense that is strongly linked to memory — it could possibly be a game changer in forensics.

In a new study published in the journal PLOS ONE, researchers examined how the sense of smell could aid victims in better identifying criminals of violent crime. Previously, using smell in forensics had been completely overlooked. But the fact is, no one smells exactly alike; our body odors are comprised of specific things like age, diet, hormonal status, and even what parasites are in our bodies. On top of that, our noses are quite smart — especially when it comes to triggering memories.

“Every individual has a unique body odor (BO), similar to a fingerprint,” the researchers wrote in their abstract. “In forensic research, identification of culprit BOs has been performed by trained dogs, but not by humans. We introduce the concept of nosewitness identification and present the first experimental results on BO memory in witness situations involving violent crimes.”

They found that smelling criminals’ odors helped people identify them 75 percent of the time, which is a significant increase from the 45 to 60 percent that people correctly identify criminals via the traditional eyewitness lineup.

“Our results suggest that humans are capable of identifying a culprit by way of odor,” the researchers added. “When the perpetrator and the victim are close to one another, as in crimes of sexual and physical assault, and especially under visually obscure conditions, an olfactory cue may be the prevailing detail.”

The researchers took body odor samples from the armpits of 20 healthy participants for the study. They then showed videos of violent crimes to 40 students, providing each with a specific odor sample. Afterward, the students were asked to sniff five different smelly glass jars, then told to identify which stench was associated with the criminal.

The authors aren’t entirely certain what made the participants associate the criminal strongly with smell, although they hypothesize that it might have to do with negative emotions during the encoding of the body odors. In a second experiment in the study, they found that associating odors with negative experiences actually enhanced participants’ ability to identify the odor again later, compared with people who had neutral experiences. This might have something to do with the fact that the sense of smell has been shown in previous research to be a strong trigger for memories — more so than any other sense. Taking a smell of a long-lost teen chapstick, for example, can take you back to a specific moment in your past — like sitting in your parents’ car as a 15-year-old on the way to summer school.

“Odors and faces are inherently different types of stimuli in several ways, and memory for odors may thus be differently influenced by emotion than memory for faces,” the authors concluded. “Although the relation between emotion and olfaction has gained considerable interest, the current study is the first, to our knowledge, indicating that negative emotion during encoding can enhance actual recognition. However, there is much to do in order to complete the picture, such as direct comparative studies of odor an visual stimuli.”

While this experiment wasn’t done in the real world, 75 percent accuracy is still pretty significant — and the researchers believe they need to explore it further.

Source: Alho L, Soares S, Ferreira J, Rocha M, Silva C, Olsson M. Nosewitness Identification: Effects of Negative Emotion. PLOS ONE. 2015.