Contactless fingerprint biometrics move towards police deployment with UK trials
The performance of software and smartphone cameras for contactless fingerprint capture is promising enough to look towards a possible launch of the technology for police in the field by 2026, attendees heard during the latest EAB (European Association for Biometrics) member lunch talk.
“Findings from pseudo law enforcement operational trials using smartphone contactless fingerprint capture technologies for search use-cases” was presented by Emily Cartledge and Guy Harris of Dstl (the UK government’s Defence Science and Technology Laboratory) and Tony Alexander of the UK Home Office.
The presentation presents findings from search trials that commenced after the Home Office’s biometrics self-enrollment trials, the findings of which were presented in an EAB lunch talk last year.
Today, the Home Office runs the “Rapid Search” capability, in which two fingerprints are collected with a contact-based scanner for biometric comparison. The move to contactless is being considered for their potential to provide the service to more officers, a decrease in costs in the absence of a requirement for a separate scanner, more choice of provider or solution for forces, and the usual advantages of contactless processes.
Harris noted that contactless fingerprint biometrics research traces back to a 2004 U.S. government initiative aimed at speeding up the collection of ten rolled prints to 15 seconds or less.
Dstl ran a proof of concept trial for contactless fingerprint capture in 2019, using the USB-connected Grabba biometric scanner as a baseline. The group found that contactless was viable, but the technology still maturing. Image quality varied significantly depending on the environment and conditions.
One observation that came out of conversations with the Home Office Biometrics User Group is that no searches have been submitted from “a large percentage of the” USB fingerprint scanners issued in the UK, suggesting that they are not being used, Harris says. Coverage is also not universal, he notes, and officers without a fingerprint scanner are generally not able to wait at a crime or investigation scene for another one with one to arrive.
The trials were carried out with Samsung Galaxy S20 devices, and app usability was their main focus, Cartledge says. Apps from five different contactless biometrics vendors were tested in scenarios involving a wide range of lighting conditions. Additional testing considered inappropriate for the trial environment, such as testing on fingers soiled with blood and dirt, were carried out in a lab environment.
The current state of contactless fingerprint capture
Notably, the presence of blood improved image quality scores, apparently improving contrast in a similar way to ink.
The overall test results, however, were mixed.
No false positive matches were recorded, and no scenarios were found to completely prevent contactless fingerprint capture from working. The fastest fingerprints were captured in a 4-4-2 method with the best-performing app was about 20 to 30 seconds, according to Cartledge.
Challenges observed include hot conditions, shaky subjects, and in some cases capture times. The interface during the capture process could also be improved, at least for some of the apps.
The most accurate app delivered a 2.2 percent false non-match rate (FNMR), similar to the Grabba device tested in 2019. The least-accurate app had a 10.6 percent FNMR. LED lighting was observed to increase the FNMR.
Dstl and Home Office Biometrics are now working on a document to specify “Technical Operational Requirements” for contactless fingerprint capturing.
Harris quoted Michael Ransom of Michigan State Police, who said that “Contactless capture is easy to do, but difficult to do well.”
The next steps for the UK’s efforts include an event next year to assess the need for training on contactless fingerprint capturing, and TOR development, and further standards development. In the meantime the Biometric Self-Enrolment Feasibility Trials, which are running in parallel, can help improve stakeholders’ understanding of the issues that come with contactless capture. “Contactless Evaluation for Law Enforcement” events are also planned for 2024 and 2025, to gain insight into training needs and improvements in performance. New vendors to the market will have an opportunity to get involved at that point.
Harris also shared a “pathway to pilot,” which posits 2026 as a target for live operational deployment of contactless fingerprint biometric capture systems.