Influence of Non-Porous Surface Topography on Forensic DNA Recovery

DNA The recovery of trace DNA from non-porous surfaces is influenced by multiple factors, including substrate characteristics, swabbing approach, and sampling conditions. Although nonporous substrates are frequently treated as a relatively uniform category in forensic DNA recovery studies, differences in surface morphology may influence the retention and accessibility of biological material during sampling. This study evaluated the influence of non-porous surface morphology on DNA recovery efficiency and STR profile quality using commonly employed forensic swabbing techniques and sampling durations. Controlled DNA deposition was performed on smooth glass, matte ceramic tile, and textured plastic surfaces. Samples were collected using wet single swabbing (W), moist-dry single swabbing (MD), and wet-dry double swabbing (WD) at sampling durations of 15 sec, 30 sec, and 45 sec. DNA extraction, quantification, and STR profiling were subsequently performed to evaluate DNA recovery efficiency, allele recovery, and profile quality. Surface morphology significantly influenced DNA recovery efficiency (p < 0.001), with smooth glass surfaces consistently producing the highest DNA recovery and STR profile completeness, whereas textured plastic surfaces demonstrated lower and more variable recovery outcomes. The MD technique produced the highest overall recovery efficiency, while the W technique generally yielded lower recovery values, particularly on textured plastic surfaces (p < 0.001). Increasing swabbing duration from 15 sec to 30 sec significantly improved DNA recovery across all evaluated surfaces (p < 0.001), whereas extending duration to 45 sec produced limited additional benefit on smoother substrates but improved recovery from textured plastic surfaces. Significant interaction effects were observed between surface morphology, swabbing duration, and swabbing technique (p < 0.05). STR profiling demonstrated greater profile completeness and reduced allele dropout on smoother substrates compared with textured surfaces. Smooth glass surfaces produced the highest mean allele recovery (96.8% ± 4.1%), whereas textured plastic surfaces demonstrated lower and more variable profile recovery (79.6% ± 11.5%). The findings demonstrate that non-porous surfaces should not necessarily be considered a homogeneous category in forensic DNA recovery studies or operational evidence collection protocols. Surface morphology may significantly influence biological material accessibility, DNA recovery efficiency, and downstream STR profile quality.