By Diego Quiroz
Operations Manager, Scottish Biometrics Commissioner
A new joint report from the Scottish Biometrics Commissioner and His Majesty’s Inspectorate of Constabulary in Scotland is turning the spotlight on how Police Scotland uses retrospective facial recognition technology – specifically, retrospective image search (RIST).
The findings show that there is an opportunity for tighter policies, more training, and a stronger focus on public trust.
Retrospective image search allows officers to match still images – say, from CCTV – to custody images stored in national police databases.
In theory, it’s a powerful tool that can help crack tough cases, protect vulnerable children online, and even spare officers from repeatedly viewing distressing material.
Police Scotland uses this technology through two key UK databases: the Police National Database (PND), and the Child Abuse Image Database (CAID).
While RIST has potential, evidence shows that between April 2023 and March 2024, Police Scotland ran 3,813 facial searches using the PND, and 193 via CAID – yet 98 per cent of those searches returned no matches at all.
This suggests that the technology’s current application may not be delivering significant operational value in the majority of cases.
For comparison, the Metropolitan Police carried out 31,078 and Greater Manchester Police carried out 5,290 searches via PND over the same period.
One of the biggest concerns flagged in the report is the absence of a specific Police Scotland policy for using retrospective image searches.
While the commissioner is satisfied about the lawfulness of RIST, it is important Police Scotland pays due consideration to the limitations of the tech, risks linked with its use (such as automation bias), or how officers can approach the necessity and proportionality test.
Specific guidance can play a key role in ensuring that officers are equipped to grapple with the complex and novel issues raised by these techs.
We also found that many images in Scotland’s criminal history system – especially those taken between 2019 and 2024 – are of poor quality or low resolution. That severely limits the reliability of the tech.
Before Police Scotland can even think about taking part in any new facial matching services proposed by the UK Home Office, including the potential use of live facial recognition technology, it needs to raise the bar on image standards.
Unlike some forces in England and Wales, Police Scotland doesn’t retain custody images of individuals who were arrested but not convicted – unless they have other prior convictions.
This helps reduce the risk of innocent people ending up in biometric policing databases.
But the report also calls for vigilance around the tech’s inner workings.
The algorithms currently used in the UK’s PND and CAID systems aren’t accredited to international forensic or scientific standards.
That raises questions about accuracy, bias, and fairness – something Police Scotland should be aware of.
Importantly, Police Scotland ensures that every facial recognition result is verified by a human before any action is taken. That’s a crucial safeguard.
Still, the report warns that new technologies should never outdo ethical reflection.
As we step further into a digital future, the challenge will be finding the right balance between public safety and civil liberties.
The report calls on Police Scotland to develop a bespoke policy on the use of retrospective image search technologies, and conduct a training needs analysis for all officers and staff regularly working in this area.
We also recommend improving the collection of data evaluating the effectiveness of such technologies and doing more to promote public understanding of its value.
These are essential issues which will strengthen public confidence, governance and oversight.
As Scotland continues to explore the role of facial recognition in modern policing, this review is a timely reminder of the interrelation of ethical, legal and social issues in new tech.