Unraveling the Impact of Pre-analytical and Analytical Factors on the Quality of Biological Evidence: A Comprehensive Systematic Review

Ensuring the quality of biological evidence is key and has become a routine requirement in forensic laboratories. The quality of biological evidence is determined by the pre-analytical and analytical phase that encompasses all procedures, starting with the crime scene to laboratory investigation of biological evidence. This is the most vulnerable part of the total testing process and a major component of the reliability and validity of results. Therefore, to generate a quality report, every biological evidence resource should be collected, maintained, and disseminated to the highest quality, based on the intended forensic use. Method: Pre-analyt-ical errors can happen at any stage prior to the testing process due to the use of insufficient or improper order of evidence collection, packaging, labelling, prolonged environmental exposure, failure to find the proper storage, the collection of evidence that is unsuitable for quality or quan-tity, inappropriate mixing of a sample, etc. Such circumstances during transportation, prepara-tion, and storage can change the outcome of forensic evidence. While analytical errors may arise in the laboratory during the processing of evidence due to mishandling, cross-contamination, and a lack of standardised procedures. Thus, employing advanced analytical methodologies, strict quality control measures, ad-herence to ethical guidelines, and appropriate data interpretation during PCR, STR profiling, and DNA sequencing are of utmost importance. The validation of quality assurance in forensic biol-ogy has been guided by a "fit-for-purpose" approach, emphasizing the suitability of methods and procedures for forensic requirements and intended applications. Pre-analytical and analytical fac-tors play a critical role in determining the success of DNA analysis and its admissibility in a court of law. To address this, this review aimed at summarizing recommendations about the pre-analytical and analytical phases and provides some guidance to reduce the effects of such factors that can have a significant impact on biological evidence.