Longitudinal Study of Forensic Evidence Quality and Criminal Justice Outcomes in Lagos State Courts: 2015-2024

The relationship between forensic evidence quality and criminal justice outcomes remains poorly characterised in African jurisdictions, limiting evidence-based advocacy for forensic science investment. This doctoral study conducts a longitudinal empirical analysis of forensic evidence quality and its association with criminal justice outcomes in Lagos State courts over a ten-year period from 2015 to 2024. A retrospective longitudinal design was employed, systematically extracting data from 500 criminal cases involving forensic evidence from the Lagos State High Court and magistrate court records, coding forensic evidence quality dimensions including documentation completeness, chain of custody integrity, laboratory accreditation status, and expert testimony quality, and applying multivariate regression analysis to model their association with conviction rates, sentence severity, and case duration. The study controls for offence type, defendant legal representation quality, and witness evidence strength to isolate the forensic evidence contribution. Findings demonstrate a statistically significant positive association between forensic evidence quality scores and conviction probability, with each standard deviation increase in quality score associated with a twenty-two percent increase in conviction odds. Chain of custody integrity and expert testimony clarity emerged as the strongest independent predictors. Temporal analysis reveals improving forensic evidence quality scores from 2020 onward, correlated with NAFDAC and police forensic unit capacity investments. The study makes an original empirical contribution establishing the quantitative relationship between forensic quality investment and justice system outcomes in a major Nigerian jurisdiction. Keywords: forensic evidence quality, criminal justice outcomes, longitudinal study, Lagos State, conviction rates.