A User-Centered Interface Enabling Secure Multimodal Biometric Search in Cross-Border Law Enforcement Operations

Abstract. Suspect identification is a critical task for Law Enforcement Agencies (LEAs) and biometric data —being inherently unique to individuals— play a pivotal role. However, the usability and interpretability
of biometric identification systems remain challenging, especially for officers with limited technical expertise. These challenges are amplified in cross-border scenarios involving multiple biometric modalities (e.g., face,
fingerprint, and voice) from heterogeneous sources. This paper presents a user-centered interface designed to support multimodal biometric matching in such complex environments. The proposed User Interface extends
a previously developed Large-Scale Biometric Indexer module, enabling efficient biometric comparisons across foreign collaborating LEAs. It supports incomplete input data, harmonises results from heterogeneous sources, and clearly distinguishes between local matches, which provide full identity details, and external matches, which initially provide only confidence scores due to jurisdictional constraints. This UI aims to bridge the gap between complex biometric processing and operational decisionmaking, ensuring that identification results are presented in an understandable and actionable manner for law enforcement personnel.