Devices such as phones, laptops, and flash drives are becoming increasingly critical to law enforcement investigations, but the reliability of the evidence from digital forensic experts has been called into question.
One study found that experts tended to find more or less evidence on a suspect’s computer hard drive to implicate or exonerate him, depending on the contextual information about the investigation provided to them.
Even those who were presented with the same information often reached different conclusions about the evidence.
Such biases are known to be a problem in other forensic disciplines, including fingerprint analysis, but this is the first time it has been demonstrated in digital forensic science.
“I cannot overstate the importance of forensic scientists understanding the potential for unintentional bias and ensuring that they take steps to minimize risks,” said Dr. Gillian Tully, professor of forensic science policy and regulation practice at the King’s College London and former UK. forensic science regulator.
Digital evidence now appears in about 90% of criminal cases. Digital examiners working in police and private laboratories use specialized software and other techniques to protect, retrieve, and analyze data from suspects’ communications, photos, and other digital interactions that could shed light on their activities.
However, the rapid growth of the field means that it has not been subjected to the same scientific scrutiny as other forensic techniques. “It has been described as the Wild West because it was not developed systematically and scientifically before it entered the criminal justice system,” said Dr Itiel Dror, an expert on cognitive bias at University College London who conducted the study.
Ian Walden, professor of information and communications law at Queen Mary, University of London, said there was a tendency to believe in the machine. “This study shows that we have to be careful with electronic evidence,” Walden said. “Not only should we not always trust the machine, we cannot always trust the person who interprets the machine.”
Dror and Nina Sunde of the University of Oslo, Norway, gave 53 digital forensic examiners from eight countries, including the UK, the same computer hard drive to analyze. Some of the examiners were only provided basic contextual information about the case, while others were told that the suspect had confessed to the crime, had a strong motive for committing it, or that the police believed he had been framed.
The study, soon to be published in Forensic Science International: Digital Research, found that examiners who had been led to believe the suspect might be innocent documented the fewest traces of evidence in the files, while those who knew of a potential motive identified the most traces.
It also found low levels of consistency between examiners who received the same contextual information, in terms of the observations, interpretations, and conclusions they drew from the files.
“Digital forensic examiners must recognize that there is a problem and take steps to ensure they are not exposed to biased and irrelevant information,” said Dror. “They must also be transparent in court about limitations and weaknesses, recognizing that different examiners may examine the same evidence and draw different conclusions.”
In its end report Before stepping down as forensic science regulator earlier this year, Tully called for better compliance with quality standards for digital forensic laboratories, many of which have not been accredited, and greater scrutiny of the scientific evidence in the courts.
Dr David Gresty, Senior Lecturer in Computer Forensics at the University of Greenwich, said: “We have every reason to believe that an expert acting in good faith, but by misinterpretation, could easily mislead a courtroom. . Without the defense directing another expert to review the evidence, this is very likely to go unnoticed and realistically undetected court errors are likely where the cases have relied heavily on digital evidence. ” .
A report published by the Police Foundation in January it recommended that digital forensics training be provided to everyone working within the criminal justice system, including judges, prosecutors and defense attorneys, to help reduce instances of misinterpretation and better understand the limits of what can be achieved .
Police Foundation Director Rick Muir said: “There can always be an element of subjectivity in this, but we could try to reduce the margin for error through effective training and the use of common standards in digital forensic work. Most of the examinations are done in-house, so I think that the police have a real responsibility to make sure that consistent rules are applied.
“If you lose credibility, it’s a huge problem because almost any criminal case these days will have some kind of digital evidence. It could free people who were wrongly convicted or guilty, and there is a broader problem of undermining the public’s trust in digital forensics if it is not done right. “
A spokesperson for the Council of National Police Chiefs said: “Digital forensics is a growing and important area of policing that is becoming increasingly prominent as the world changes. This report comes from a very small sample and is not representative of the operational environment in which the police in this country operate. We are always looking at how technology can increase our digital forensic capabilities and a national program is already working on this. “
George is Digismak’s reported cum editor with 13 years of experience in Journalism