A 22-year-old woman presents after being sexually assaulted. She reports that she was bitten and strangled by the perpetrator during the assault. The patient has bruising to her face and a semi-circular bruise on her chest. She has faint petechiae on her face but no bruising is evident on her neck. The forensic nurse is called and brings a sexual assault evidence kit and an alternative light source to the room. The patient’s primary nurse asks you what the purpose of the alternative light source (ALS) is.

Introduction

Forensic science plays a pivotal role in emergency medicine, especially when physicians are called upon to document injuries in the medical record or provide testimony in legal proceedings. However, several forensic techniques historically used to guide clinical and legal decisions have come under scrutiny due to their lack of scientific validity. The use of invalid forensic methods has directly contributed to wrongful convictions in criminal cases. This article discusses four such debunked topics—bite mark analysis, dating of bruises, use of alternative light sources for injury identification, and the shaken baby triad.

Bite Mark Analysis

Bite mark analysis has long been treated as a way to link an injury to a specific person, but it is highly subjective and vulnerable to error. Skin is an elastic medium that distorts easily, and studies have demonstrated poor reliability and reproducibility in bite mark measurements and comparisons. The National Academy of Sciences and the Innocence Project have both criticized bite mark analysis, noting its lack of objective standards and role in wrongful convictions. Recent consensus among forensic experts is that bite mark analysis should not be used to identify suspects or serve as evidence in court, especially in the absence of corroborating data. However, bite marks should still be swabbed for DNA evidence.

Dating of Bruises

Emergency physicians are sometimes asked to estimate the age of bruises, especially in suspected abuse cases. In the past, physicians relied on bruise color and appearance to estimate the time that an injury occurred. Bruises do change color over time as the initial inflammation from the trauma fades and the extravasated hemoglobin breaks down, resulting in a brown or yellow bruise. However, studies have shown that bruise evolution varies widely depending on multiple factors, including skin tone, injury mechanism, and individual healing responses. No reliable method exists for accurately dating bruises, and attempts to do so may lead to erroneous conclusions. Guidelines from the American Academy of Pediatrics and peer-reviewed research recommend against using bruise color as an indicator of injury age.

Alternative Light Sources for Injury Identification

Alternative light sources, which emit light at varying wavelengths, have been promoted as tools to enhance the visualization of injuries, including bruises and bite marks. Following the publication of a single methodologically flawed study, many forensic nurses used ALS to detect “subclinical” bruising; that is, bruises not visible to the naked eye under standard lighting. Recent research indicates that ALS-induced fluorescence cannot accurately be used to diagnose subclinical bruising. False positives are common, and ALS findings are highly dependent on operator technique and environmental factors.

The Shaken Baby Triad

The shaken baby triad refers to the presence of subdural hematoma, retinal hemorrhages, and encephalopathy, which is historically considered indicative of abusive head trauma. Recent studies have challenged the specificity of this triad. Evidence shows that these findings can result from a variety of etiologies, including accidental trauma, underlying medical conditions, and birth-related injuries. Current guidelines stress the importance of comprehensive evaluation and warn against attributing these findings solely to shaking without additional evidence. The medical community now recognizes the need for multidisciplinary assessment (child protective services, child abuse pediatrics, law enforcement, social services, and children’s advocacy center) and greater caution in making abuse diagnoses based on this triad alone.

Conclusion

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Emergency physicians must be aware of the limitations and controversies associated with certain forensic science techniques. Reliance on debunked methods such as bite mark analysis, bruise dating, ALS-based injury identification, and the shaken baby triad can lead to misdiagnoses, wrongful accusations, and unjust legal outcomes. When evaluating injury cases, physicians must commit to evidence-based practices, meticulous documentation, and active collaboration with forensic specialists. Continuing education and awareness of evolving forensic standards are essential for ethical and effective patient care.

Case Resolution

After collecting swabs from the bite mark as well as the rest of the sexual assault evidence kit, the forensic nurse informs you that the patient has some bruises on her neck which she noted with use of the ALS. You re-evaluate the patient and once again do not note bruising on the patient’s neck. You explain to the forensic nurse and to the patient’s primary nurse why an ALS should not be used to diagnose “subclinical bruising,” and arrange follow-up for further forensic photos should bruising become visible in the next few days.

Dr. Riviello is professor and chair of emergency medicine, UT Health San Antonio.

Dr. Rozzi is an emergency physician, medical director of the Forensic Examiner Team at WellSpan York Hospital in York, Pennsylvania, and secretary of ACEP’s Forensic Section.

References

1. National Academy of Sciences. Strengthening Forensic Science in the United States: A Path Forward. Washington, DC: The National Academies Press; 2009.
2. American Academy of Pediatrics. Evaluating Children With Suspected Physical Abuse: Bruising and Skin Injuries. Pediatrics. 2020;145(4):e20200347.
3. Innocence Project. Bite Mark Evidence. https://innocenceproject.org/wp-content/uploads/2020/04/Description-of-bite-mark-exonerations-and-statistical-analysis_UPDATED-04.09.2020.pdf
4. Thompson, R. M., et al. Reliability of Bruise Dating in Child Abuse Cases. JForensic Sci. 2013;58(5):1208-1213.
5. Lombardi M, Canter J, Patrick PA, Altman R. Is fluorescence under an alternate light source sufficient to accurately diagnose subclinical bruising? J Forensic Sci. 2015;60(2):444-449.
6. Geddes, J. F., et al. Shaken Baby Syndrome: A Critical Review. Lancet. 2001;358(9297):1551–-557.
7. Leventhal, J. M., et al. The Shaken Baby Syndrome: Diagnostic Pitfalls. Pediatrics. 2018;141(5):e20173462.