University of Adelaide researchers are studying the reliability of eyewitness identification testimony in criminal cases in the hopes of improving evidence from witnesses and leading to fairer trials.
Previous studies from the United States show that 70% of people wrongfully convicted of a crime had been convicted on the basis of eyewitness testimony, which is often unreliable and can be distorted by a range of factors, such as subtle cues from police.
Researchers from the University of Adelaide's School of Psychology are focusing their efforts on the difference between objective and subjective testimony. They're finding that despite many eyewitnesses having poor subjective memories, they often have a good memory for objective details, such as distance.
"Estimates of distance – such as how far an eyewitness was standing from the crime being committed – and the time taken to witness the crime are less prone to distortion than other details," says the leader of the project, Dr Carolyn Semmler, a Senior Lecturer in the School of Psychology.
"Unlike subjective judgments, correct answers exist for objective judgments. Our research aims to explain why objective judgments seem to be relatively immune to the same kinds of clouded memory problems that affect other details in eyewitness testimony."
Psychology PhD student Adella Bhaskara has been studying 700 people's responses to distance estimates in a mock crime scenario.
"Our participants are exposed to a 'mock' criminal and are asked to provide details of what they saw, both immediately afterwards and also again after a delay of one week. Distance estimates are the strongest part of their recollections," Ms Bhaskara says.
"This is effectively a laboratory experiment, but it is a step closer to a real-world evironment, which makes it more legally relevant. It's also one of the few times anyone has used an actual 'target' to study eyewitnesses' distance estimates, so we believe it will provide some insights that can be translated to real-world situations," she says.
Dr Semmler says: "By providing a theoretical understanding of the processes involved in the reliability of evidence from witnesses, we aim to suggest practical reforms that will help to optimise that evidence.
"Our insights should be equally useful for the prosecution as well as defence.
"Ultimately, we hope that what we learn will help to reduce the rate of wrongful convictions, paticularly where the weighting of evidence is on eyewitness testimony."