Poor quality images hold Scottish police facial recognition matches to 2%

Scottish Biometrics Commissioner Dr. Brian Plastow warns that a significant number of the custody images held in national police databases are too poor quality for effective face biometrics matching.

A joint assurance review report from Plastow and His Majesty’s Inspectorate of Constabulary in Scotland (HMICS) says that a “sizeable portion” of images collected between 2019 and 2024 are unusable for forensic facial recognition.

Police Scotland confirmed it is aware of the issue, and says it will consider the four recommendations offered in the report.

The Commissioner and HMICS repeated Plastow’s recommendation that Police Scotland “develop a bespoke policy” for retrospective biometric searches against the Police National Database (PND) or the UK Child Abuse Image Database (CAID), with specific guidance for scope, legal and ethical use, retention periods, training, community engagement and other factors. The report also recommends improving the resolution of custody images before joining the UK Home Office Strategic Facial Matching Project, and analyze any need for training of its staff. The force should also improve its data management and analysis to enable it to determine how effective and efficient its face biometrics use is.

So far, only 2 percent of Police Scotland’s face biometrics searches return a potential match, and “This suggests that the technology’s current application may not be delivering significant operational value in the majority of cases,” the report states. Police tried 4,006 times in 2023-2024.

The PND uses an algorithm developed by Cognitec, and was upgraded to FaceVACS-DBScan ID 5.5.0 in November, 2021. The report reviews the algorithms’ performance in testing by NIST, and the importance of knowing the algorithms’ characteristics and any disparities for matching people from different demographics.

Police Scotland are addressing the first recommendation already, with a comprehensive biometrics policy document expected by October 31, 2025. The report suggests that the policy should enhance the governance structure for PND users.

A review of PND use states that the Metropolitan Police searched the biometric database more than 31,000 times during the 2023-24 year, Greater Manchester Police searched it 5,290 times, and South Wales Police conducted 1,727 searches.

The report concludes with a review of future challenges. Chief among them may be the consideration of whether and how to adopt the Strategic Facial Matching Project the Home Office Biometrics Programme is currently implementing. Joining the project could give Police Scotland access to operator-initiated facial recognition and live facial recognition, as well as an updated algorithm for retrospective searches, but the report suggests there are issues which need to be taken care of before any new biometric technology is adopted.

Article Topics

biometric data quality  |  biometric matching  |  biometrics  |  face biometrics  |  facial recognition  |  police  |  Scotland  |  Scottish Biometrics Commissioner