Poor-quality Police Scotland photos mean crimes 'could go undetected', as 98% of database searches fail
Force urged to remedy shortfalls before any wider use of facial recognition technology
Crimes across Scotland could be going undetected because of the poor quality and resolution of custody photographs taken by police of people they arrest, a watchdog has warned.
A “sizeable proportion” of images taken by Police Scotland between 2019 and 2024 are of such low quality, they are unsuitable for use by the force in facial searching technology software, according to the Scottish biometrics commissioner Dr Brian Plastow.
A newly published joint assurance review of the national force’s use for retrospective facial search technologies found the technological limitations had created a “gap” that meant some images were not being detected when officers searched the UK-wide police national database (PND).
“This gap could mean that people who have had their custody image previously taken are not being detected on future probe images uploaded by Police Scotland, which could lead to crimes not being detected,” the report warned.
The force has been told it must improve the resolution of its custody images before it can take part in any new facial matching technology initiatives, including the potential use of contentious live facial recognition technology.
Police forces across the UK upload images of everyone they arrest to the PND - a database containing more than 19 million custody images. This allows officers to detect potential matches with photographs of suspects captured and uploaded from sources, including video doorbells and CCTV. The system can lead to a person arrested for one crime being linked to unsolved crimes.
But the new report flagged the “insufficient quality and resolution” of images in Police Scotland’s criminal history system, meaning many images were not searchable via the PND.
The joint assurance review, carried out in conjunction with His Majesty’s Inspectorate of Constabulary in Scotland, found Police Scotland carried out 3,813 facial searches via the PND between April 2023 and March 2024.
But about 98 per cent of searches failed to produce any potential matches, raising questions. “This suggests that the technology’s current application may not be delivering significant operational value in the majority of cases,” the report added.
It states that Police Scotland said a “software issue” was causing the custody images to be captured at a lower than recommended minimum size. The images were then being additionally compressed using a technique that left them unsuitable for use within the PND for facial searching purposes.
Dr Plastow said: “Extreme caution must be exercised with any retrospective ICT fix to uncompress these images. If they cannot be fully restored to their original format, the reliability of the data could be significantly compromised.”
Scottish Liberal Democrat justice spokesman Liam McArthur, who has scrutinised the force’s proposed use of facial recognition technology, said: “This report reflects the importance of getting the basics right before rushing ahead with new technology like live facial recognition, where there are also serious concerns about invasion of privacy and mistaken identity.”
Police Scotland’s Assistant Chief Constable, Steve Johnson, said: “We will consider the Scottish Biometrics Commissioner’s recommendations in full, and in the context of the development of our biometrics strategy, policy and standard operating procedures.
“Our biometrics oversight board is already aware of this issue and is overseeing work to improve the quality of images taken in custody and the collaboration with the Home Office strategic facial matcher project, which mirrors the recommendations.”