Empirical Investigation of Forensic Evidence Destruction and Tampering in the Nigerian Police Force

The destruction and tampering of forensic evidence by law enforcement personnel constitutes a serious threat to the integrity of the criminal justice process, yet remains poorly empirically characterised in the Nigerian context. This study conducts an empirical investigation of the prevalence, mechanisms, and contributing factors of forensic evidence destruction and tampering within the Nigeria Police Force. A mixed-methods empirical design was employed, analysing 180 criminal appeal and review cases from five geopolitical zones in which evidence tampering was alleged between 2019 and 2024, administering anonymised surveys to 200 police officers across twelve states to assess institutional culture and incentive structures around evidence handling, and conducting in-depth interviews with twenty-two reformed and serving officers and twelve defence lawyers. The study applies a corruption opportunity theoretical framework to model the structural conditions enabling evidence tampering. Findings confirm substantiated evidence tampering allegations in forty-one percent of reviewed appeal cases, with biological and documentary evidence being the most frequently targeted categories. Anonymous officer surveys reveal that institutional pressure to secure convictions was acknowledged as a driver of evidence manipulation by sixty-three percent of respondents. Structural factors identified include inadequate evidence storage security, limited audit mechanisms, and low probability of detection and sanction. Recommendations include the introduction of chain of custody digital audit systems with tamper-evident logging, independent evidence storage facilities separate from investigative units, and mandatory integrity training supported by consequence management reform. Keywords: evidence tampering, forensic integrity, Nigeria Police Force, criminal justice, corruption.