Fingerprints and DNA are crucial to securing criminal convictions. But forensic investigators of the future may have another form of evidence to nab perpetrators - the way they move.
University of New England researcher Dr Justin Gaetano believes that each person's movements and gait - their "body motion profile" - can be every bit as unique as a fingerprint.
"From a limp to fallen arches and poor posture, these little quirks in our motion are very revealing," Justin said. "They are especially useful when voice and facial evidence is absent or ambiguous. I would like to see body motion become a greater part of forensic psychology, so that when law enforcers round up a list of suspects, those individuals are asked to move. These movements can then be compared to observations reported by victims and witnesses or captured by CCTV footage."
Justin specialises in person perception - how we combine all sorts of multisensory cues (impressions of sex, race, age, emotional state and even gestures) to build a picture of those around us and guide how we respond to them. Often this "profile" is incomplete, and movements can help to bolster our impression of a person's identity, character and intentions.
"There are some movement signatures that are either more feminine or more masculine," Justin said. "They allow us to make some educated guesses about a person's gender. On top of that, movement can show emotion - whether someone is happy or angry, sad or fearful."
This emerging field of psychology also includes phenomena deeply rooted in our evolution, including the male bias ("when senses fail, better guess male") and other-race effect - the fact that we are more prone to making errors in identifying someone from a different ethnic group.
"These factors have huge implications for the identification of perpetrators but also the likelihood of someone becoming a victim," Justin said. "Psychopaths can be very accurate in identifying people who were vulnerable or weak, and therefore better targets, by the way they move."
"I am hoping this research can translate into more practical forensics, to increase the accuracy of the identification of criminals and ensure we don't end up prosecuting innocent people, but also to protect potential victims."
As well as being of practical help to police, Justin believes that better understanding human movement could be useful to tactical response, anti-terrorist and air security officers. "Essentially, it's helpful to anyone seeking to protect themselves or the community from harm," he said.