Developments in Forensic Genetics

Forensic Genetics is a new discipline. The use of DNA in police cases began properly in 1983 with a UK case which identified the murderer due to a distinctive DNA feature.  More on that case here. In the early days, DNA profiling was only just more accurate in identifying people than blood typing, and fingerprints were more trusted by the juries. In more recent times, a jury demands hard DNA evidence due to watching their favorite crime shows, often called the ‘CSI effect’ (Dakss, 2005).  But there are recent developments in forensic genetics.

What is forensic genetics?

Forensic genetics belongs in the category of forensic medicine. Forensic means as applicable in a court of law. Genetics is the study of inherited characteristics. So, forensic genetics is therefore the studying the uses of inheritable characteristics to work out an answer to legal issues (Davis, 2024).  While most people think DNA is best used to work out who committed a crime, its most important work is pointing out who is not the potential criminal. Another application of forensic genetics is paternity testing in cases where requests for child support end up in court (Schneider, 2006).

How has forensic genetics evolved?

Before DNA

First of all, even before DNA testing appeared, a crude form of forensic genetics existed as blood phenotyping. Markers in the blood, such as grouping and human leucocyte antigen (HLA), are all part of genetic screening, even if they were not considered as such at the time (Davis, 2024). In 1901, Karl Landsteiner explained why mixing two people’s blood sometimes led to clumping, as shown in figure 1.

Image 1. Blood Typing
Credit: Bondarev.gal, CC0, via Wikimedia Commons

His work on blood groups led directly to successful blood transfusions (NobelPrize.org, 2024). These methods were difficult to apply to forensics because of the large amounts of blood needed to perform the tests. The discovery of HLA in the 1960s was again stymied by the need for large amounts of blood, so was used solely for paternity testing, not for criminal work.

With the discovery of DNA

By the 1980s the amounts of blood required had decreased, but monoclonal antibodies still required a fresh, not dried, source (Carracedo, 2013).  When Professor Alec Jeffries presented his paper on Short Tandem Repeats in the mid-1980s, it was a breakthrough for forensic genetics (Saad, 2005). The utilization of his techniques to clear a man of murder, and later convict a different suspect, made forensic genetics an important tool in the crime-solving kit (Butler, 2010).  At that time, DNA could only differentiate between individuals. However, since the Human Genome Project produced a map of the entire human genome in 2003, scientists have worked out how to relate the genes to human development (Freidovich-Keil, 2024).

Advances in DNA techniques

The first characteristic scientist could work out from DNA analysis allowed them to identify the sex of human remains. More recently, scientists have located genes that code for other parts of the body that aid giving a name to human remains.

Image 2. A microbiology prepares DNA samples.
Credit: The U.S. Food and Drug Administration, Public domain, via Wikimedia Commons

By 2008, scientists had picked up on genes that expressed red hair color and also genes for impulsivity, ADHD, weight, life length, and some common inherited diseases (Randerson, 2008).  The rapid advances continued, so that in 2018 a multi-national team of scientists developed a method of testing for the pigment in hair, eye, and skin color (Aisen, 2018). All of these discoveries help in forensic investigations.

How does all this relate to solving crime?

Facial DNA phenotyping

Now it is possible to match hair, eye, and skin color, the logical focus is on trying to produce an image of the person from their DNA. This dream of DNA phenotyping would put a name to skeletal human remains in missing-person cases. Of course, this is still fiction (Dawson, 2015). In JD Robb’s Concealed in Death, a near-future police procedural set in AD2060, the forensic scientists can determine even the race of the victim, but they still require the help of facial reconstruction specialists, working from the skull, to produce faces for their victims (Robb, 2014). Back in real life, it’s not just DNA that shapes the face, environment and circumstance both play a major role. It will take a serious advance in the technology and interpretation before we are to the point where DNA can create a picture-perfect image of the person (Sero, 2019).

Forensic Genealogy

One of the most encouraging uses of forensic genetics has come from the even newer discipline of Forensic Genetic Genealogy.  Many of the ancestor-hunting sites have extensive DNA databases, providing a huge wealth of genetic information that allows the users to trace their family history, and locate relatives lost in time. But when using these databases in hunts for long-lost murderers, law enforcement runs into problems with consent. In fact, 23andme states that it will resist attempts by police to use its database in their hunt for past criminals (Reji, 2024).

How does it work?

Figure 3 offers a rough idea of how Forensic Genealogy works.

Image 3: Two Family Trees interlink.

The police obtain a warrant to upload the unknown DNA (shown as green triangle U) to the genealogy tracker’s database. Partial matches are found in cousins A and B. By creating a family tree, the Genealogy specialist can trace suspect C.

Case Study 1

In 1985, 22-year-old Terri McAdams was murdered in Arlington, TX.  No one was charged with the crime, but multiple times investigators have revisited the case, in the hope that forensic developments could help solve the mystery.  In 2021, articles from the crime scene were sent for DNA analysis (Ciesco, 2024). If stored correctly, DNA can remain viable for testing for decades (Zhang, 2024). This time, the forensics produced a profile of an unknown male. He was not on any criminal database, and investigators thought they would have to set the case aside again. Then someone suggested the new discipline of Forensic Genealogy. Using the extensive genealogy charts, they discovered Bernard Sharp, involved in a murder/suicide 9 months after the murder of Terri McAdams. While he was never brought to justice for his crime against Terri McAdams, her family can be reassured that her murderer was uncovered (Ciesco, 2024).

Case Study 2

In 1987 a couple, Tanya Van Cuylenburg and Jay Cook, from Vancouver Island were found murdered in Washington state. DNA evidence was from an unknown person and the case lapsed. In 2018 the case was reopened and used a Genealogy website. This uncovered 2 partial matches, and tracing the family tree found a marriage between a cousin of each of the people. The son of this union, William Earl Talbert II, had lived near to where the murders took place. He had no record of contact with the victims and was previously free of criminal accusations (Reji, 2024), but he was arrested and convicted of their murders (Staff, 2022). A powerful case for Forensic Genealogy.

Conclusion

Forensic Genetics helps identify skeletal remains and give families closure on their missing loved ones. Even after decades, the collection and analysis of DNA helps to solve cases that have gone cold. With the continued improvement of the techniques, maybe the production of facial phenotypes from DNA will eventually move from Science Fiction to science fact.

References

Aisen, C.F., (2018). New Tool Predicts Eye, Hair and Skin Color from a DNA Sample of an Unknown Individual. News at IU Indiana University. 14 May. https://news.iu.edu/live/news/25053-new-tool-predicts-eye-hair-and-skin-color-from-a

Butler, J. M. (2010). Fundamentals of Forensic DNA Typing. London: Academic Press. https://aboutforensics.co.uk/colin-pitchfork/

Carracedo, A., Seigal, J.A. (ed) and Saukko, P.J. (ed) (2013).  Forensic Genetics: History. Academic Press, Elsevier Ltd. London. p207. https://books.google.co.uk/books?hl=en&lr=&id=VYJdLSVW7bMC&oi=fnd&pg=PA206&dq=history+of+forensic+genetics&ots=XdcD93SEct&sig=EoNMiUgN0Jjr0FlveVhv3z0cdh4#v=onepage&q=history%20of%20forensic%20genetics&f=false

Ciesco, T. (2024). Arlington Pd, Fbi Solve 1985 Cold Case Using Investigative Genetic Genealogy.  MyArlingtonTx. 14 August. https://www.arlingtontx.gov/news/my_arlington_t_x/news_stories/arlington_p_d__f_b_i_solve_1985_cold_case

Dakss, B. (2005) The CSI Affect. CBS News. https://www.cbsnews.com/news/the-csi-effect/

Davis, C.P. (2024). Definition of Forensic Genetics. RxList. https://www.rxlist.com/forensic_genetics/definition.htm

Dawson, J. (2015). Defining a Face: What Can DNA Phenotyping Really Tell Us About An Unknown Sample. National Institute of Justice. 31 August. https://nij.ojp.gov/topics/articles/defining-face-what-can-dna-phenotyping-really-tell-us-about-unknown-sample#:~:text=Scientists%20can%20now%2C%20with%20some,as%20skin%20pigmentation%20and%20ancestry

Freidovich-Keil, J.L., (2024). Human Genome Project. Britannica. 24 September. https://www.britannica.com/event/Human-Genome-Project

NobelPrize.org. (2024). Karl Landsteiner – Facts.  Nobel Prize Outreach AB. Mon. 30 Sep. https://www.nobelprize.org/prizes/medicine/1930/landsteiner/facts/

Randerson, J. (2008). What DNA Can Tell Us. The Guardian. 27 April. https://www.theguardian.com/science/2008/apr/27/genetics.cancer#:~:text=Sex,(which%20makes%20them%20female)

Reji, S. and Salunkhe, P. (2024). Forensic Genealogy in Solving Age-Old Cases: Review. International Journal for Multidisciplinary Research (IJFMR). Volume 6, Issue 2, March-April . https://www.ijfmr.com/papers/2024/2/17279.pdf

Robb, R.D. (2014). Concealed in Death. Piatkus (Little, Brown Book Group). London.

Saad R. (2005). Discovery, development, and current applications of DNA identity testing. Proceedings (Baylor University. Medical Center), 18(2), 130–133. https://doi.org/10.1080/08998280.2005.11928051

Schneider, P.M. (2006). Scientific Standards for Studies in Forensic Genetics. Forensic Science International 165 (2007) 238–243. 27 July. https://avys.omu.edu.tr/storage/app/public/kokdener/122131/1.pdf

Sero, D., Zaidi, A., Li, J. et al. (2019). Facial recognition from DNA using face-to-DNA classifiers. Nat Commun 10, 2557. https://doi.org/10.1038/s41467-019-10617-y

Staff. (2022). U.S. court reinstates guilty verdicts in 1987 killings of Vancouver Island couple. CTV News Vancouver Island. 24 Dec. https://vancouverisland.ctvnews.ca/u-s-court-reinstates-guilty-verdicts-in-1987-killings-of-vancouver-island-couple-1.6208022

Zhang, L. (2024). How long does DNA stay on clothes? The Tech Interactive. 24 June.  https://www.thetech.org/ask-a-geneticist/articles/2024/dna-on-clothes/