Trauma Memory Testimony Corroboration and Mental Health Symptom Persistence in Rwandan Gacaca Archive Cohorts: A Target-Trial Emulation of Evidence Verification Timing

The timing of corroboration of survivor testimony in post-conflict legal archives has been proposed as a determinant of long-term mental health trajectories, yet the causal estimand is poorly defined and the design operating characteristics of any evaluation remain uncharacterised. The design parameters were a between-cluster standard deviation of 6.0, a residual standard deviation of 4.5, and an intraclass correlation of 0.640; power was estimated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The analysis indicates that 54 clusters are required to detect a 5 percentage point effect at 80% power. The framework clarifies the conditions under which archive-based target-trial emulation can support causal inference about verification timing, and identifies the cluster counts at which the BACI estimator attains conventional power thresholds.