In criminology, forensic investigators have used DNA analysis for some time. They apply genetic analysis to solve crimes where biological materials serve as evidence. This type of analysis remains a powerful forensic tool despite its drawbacks. Advances in DNA testing have made it so precise and highly sensitive that handlers risk contaminating samples (Butler, 2015). Environmental damage can also render DNA useless as a forensic tool. In such cases, conducting a genomic analysis of the entire genome helps as a control. Even with its high sensitivity and reliability, forensic experts have encountered cases where authorities falsely imprisoned or released suspects due to faulty or contaminated evidence.

Historically, forensic teams have used genetic and genomic samples to catch criminals and exonerate the innocent. In the well-publicized case of Joseph James DeAngelo, the Golden State Killer, investigators used consumer DNA testing to compare forensic evidence with familial DNA (Wikipedia contributors, 2025). The company’s privacy policy in DNA analysis prevented this type of use. However, the investigators used evidence to create a fake profile and matched their evidence with that of DeAngelo’s family member, a service user. Although their methodology was unethical, they matched the evidence to DeAngelo, leading to his arrest (St. John, 2020). Investigators can use familial lines to convict criminals effectively, provided they compare evidence against an ethically maintained database.

Conversely, DNA evidence has played a crucial role in exonerating the innocent. Authorities convicted Kirk Bloodsworth, a U.S. Marine, of rape and murder, sentencing him to death based on circumstantial evidence. Investigators believed he was responsible for the murder of a 9-year-old girl. However, after Bloodsworth spent nine years in prison, forensic analysts compared DNA from the crime scene with his and the victim’s, proving his innocence (The Innocence Project, 2025). Cases like these punctuate the importance of genetic testing in criminology.

Forensic scientists retrieve genetic evidence from various sources, including non-visible biological material left on surfaces through skin contact (Alketbi, et al., 2025). Today, investigators primarily use trace samples of biological material in evidence-gathering. They extract and amplify DNA from these samples, achieving an overall success rate of 64% (Alketbi, et al., 2025). Although different surfaces yield varying degrees of success, most samples remain viable as evidence. While forensic teams predominantly use trace samples in criminal investigations, they also rely on them to identify disaster victims and exonerate falsely accused individuals. However, such small samples remain highly vulnerable to contamination or environmental degradation.

Dr. Edmond Locard, known as the “Sherlock Holmes” of Lyon, France, developed the exchange principle, which states that “every contact leaves a trace.” His principle asserts that every criminal leaves something behind at a crime scene, forming the foundation of modern forensics, particularly DNA forensics (Naqvi, et al., 2024). Today forensic analysts have refined their techniques to such a degree that they can extract DNA evidence from trace amounts of biological material. Although these traces remain invisible to the eye, biological material is present whenever someone touches a surface. Environmental elements pose a high risk of DNA degradation, with exposure to water, temperature fluctuations, humidity, UV radiation, and time affecting the sample. Among these factors, extreme temperatures and UV radiation present the most significant threats to DNA evidence (Naqvi, et al., 2024). In light of these facts, forensic teams must secure samples as quickly as possible after discovery.

DNA forensics has revolutionized criminal investigations, providing a powerful tool for both convicting the guilty and exonerating the innocent. Genetic and genomic analysis advancements have enhanced forensic precision, allowing investigators to extract valuable evidence from even trace biological material. However, the heightened sensitivity of DNA testing introduces risks, including contamination and environmental degradation, which can compromise results. Ethical concerns also arise in familial DNA search cases, emphasizing the need for responsible forensic practices. Despite these challenges, DNA evidence remains a fundamental element of modern criminology, reinforcing the importance of meticulous handling, ethical application, and continued advancements in forensic science.

References

Alketbi, S. K., Goodwin, W., Alghanim, H. J., Abdullahi, A. A., Aidarous, N. I., Alawadhi, H. M., . . . Almheiri, M. A. (2025). Trace DNA Recovery: Insights from Dubai Police Casework. Perspectives in Legal and Forensic Sciences; 2(1):10001, https://doi.org/10.70322/plfs.2025.10001.

Butler, J. M. (2015). The Future of DNA Analysis. Phil. Trans. R. Soc. B; 37020140252, http://doi.org/10.1098/rstb.2014.0252.

Naqvi, S. Z., Ahmed, U., Daga, S. S., Rawat, P., Singhal, G., & Patil, B. (2024). Examining the Impact of Environmental Variables on DNA Extraction Efficiency in Forensic Blood Samples. Periodico di Mineralogia; 93 (5), 440-458.

St. John, P. (2020, 12 08). The untold story of how the Golden State Killer was found: A covert operation and private DNA. Retrieved from LA Times: https://www.latimes.com/california/story/2020-12-08/man-in-the-window

The Innocence Project. (2025, 02 09). Kirk Bloodsworth. Retrieved from Innocence Project: https://innocenceproject.org/cases/kirk-bloodsworth/

Wikipedia contributors. (2025, 01 12). Joseph James DeAngelo. Retrieved from Wikipedia: https://en.wikipedia.org/w/index.php?title=Special:CiteThisPage&page=Joseph_James_DeAngelo&id=1268931776&wpFormIdentifier=titleform