Limitations of Forensic Serology in Sexual Assault Cases
Introduction
In forensic serology, identification of biological fluids such as semen, blood, saliva and vaginal secretions are frequently discovered in cases of sexual assault. Claims of physical contact between suspects and victims may be substantiated by these biological markers (Schiwietz et al., 2020). Serology has some serious drawbacks despite its usefulness. Its efficacy is compromised by a number of factors, including sample deterioration, false preliminary testing, spermatozoa absence, improper procedure handling, backlog of untested kits, cognitive biases, and technological differences between labs. This review looks at these issues and offers solutions to improve the delivery of justice and forensic results.
Biological Evidence Degradation
Due to time gaps before collection, in many sexual assault cases the biological fluids degrade rapidly which is often caused by emotional trauma or social stigma (Schiwietz et al., 2020). Within 24 to 48 hours, high temperatures, humidity, and microbial activity significantly deteriorate sample quality and lower the sensitivity of the acid phosphatase test (Schiwietz et al., 2020). Furthermore, false negative results are often produced by evidence kits that are not properly preserved or that are analyzed too slowly (National Institute of Justice, 2020).
False Positives in Presumptive Tests
Presumptive tests are popular as they are quick and easy, but they can result in false positives. For example, acid phosphatase may react with vaginal secretions, plant debris, and cleaning agents in addition to semen (Khurana et al., 2024). Such results can be deceptive if not supported by confirmatory testing. Relying solely on presumptive results can lead to wrongful suspicion or unnecessary investigative efforts. Therefore, presumptive tests must always be followed by confirmatory methods.
Lack of Spermatozoa
Conventional microscopy is useless if there are no sperm cells because of azoospermia, condom use, or previous vasectomy. Although they are not always accessible, indicators such as PSA and semenogelin provide an additional form of confirmation in certain situations (National Institute of Justice, 2020). Accurate case conclusions may be hampered by limited access to these confirmatory assays.
Errors in Procedure and Chain of Custody
Appropriate methods for collection, transportation, and storage are essential for accurate serological results. Samples may be declared invalid in court due to contamination, labeling errors, or missing documentation—breaks in the chain-of-custody (Ledray, 2005). These hazards are increased when forensic examiners are not properly trained.
Sexual Assault Kit Backlog
Due to resource constraints, sexual assault kits are frequently left untested. Serological and DNA tests are delayed in many areas since thousands are kept unanalyzed (Campbell et al., 2015). Investigations become more difficult as backlog samples lose their evidentiary value over time.
Cognitive Bias and Mistakes in Interpretation
Bias risk is introduced by human interpretation. Research shows that erroneous convictions have been caused by confirmation bias and incorrect interpretation of mixed-DNA profiles (Fenton et al., 2020). Blind analysis and objective procedures are essential to reducing these hazards.
Technological Gap and Emerging Solutions
New developments such as improved PSA detection techniques and LAMP-based assays promise increased speed and sensitivity (Schunkul, 2025). However, widespread adoption remains limited, particularly in forensic labs with limited funding.
Conclusion
Investigations into sexual assault continue to depend heavily on forensic serelogy. Its drawbacks, including bias, backlog delays, missing spermatozoa, deterioration, false positives, and unequal access to technology, must be addressed. It is crucial to put in place prompt evidence handling, improved confirmatory techniques, improved training, and system improvements. Such improvements will support forensic integrity and contribute to more equitable court decisions.
