How Forensic Scientists Are Reconstructing Faces Using DNA Found At Crime Scenes

A forensic scientist crouches down on a dirty factory floor. There’s a pool of blood, and they delicately dip a swab into it before placing it carefully into a labeled sample bag. This swab will soon make its way to a sterile laboratory, where it will be processed, and from it, a face will emerge. The face of the person the blood belonged to.  

This isn’t science fiction. This is DNA phenotyping: a real, rapidly developing technology already being used in some criminal investigations. It’s the art (and science) of reconstructing human facial features using DNA from forensic samples.

How does it work?

The way you look is a combination of unique and inherited characteristics, along with some environmental influences (like braces, scars, or dyed hair). Forensic scientists have started using DNA found in samples to figure out what the person it belonged to looked like.

This is called DNA phenotyping and is a complementary method to other forensic investigation methods. The technique relies on two components: the first is the genotyping tool, which allows DNA analysis of samples, and the second is a prediction tool based on validated prediction models, which can be used to estimate appearance. 

Scientists use the genetic code found in the DNA to predict an organism’s features. The sample that is found undergoes DNA sequencing. The information gained from this is able to predict an organism’s physical traits, with the right expertise and knowledge. It can be used to determine hair color (if not tampered with hair dye) and eye color, for example. 

In forensics, indirect methods are used, which involve variants associated with genetic components of ancestry. These are often single-nucleotide polymorphisms (SNPs), which can act as ancestry informative markers (AIMs). 

A forensic scientist can look at the SNPs found in a sample and attribute these to physical appearance. They will then use complex algorithms to combine the data from the sequencing and reverse engineer an image of the person who produced the sample.  

This method is useful when the donor is not known to investigative authorities. It is hoped that this technology can produce new leads for authorities. 

What are the challenges?

There are a few ethical concerns with this methodology. One is that DNA phenotyping is not always accurate, which could lead to false identification.

There are also many ways for a person to change their appearance from what their genetics predict. Braces can change facial shape, and cosmetic procedures and surgeries can change what a person looks like. 

There is also another issue with the ethics of this technique. There is a concern that AIMs could be used in a way that encourages law enforcement to stereotype suspects, or that the database used for reference could be biased, so that some populations could be over- or underrepresented. 

DNA phenotyping can help solve murders

The first ever case in which this methodology was used was the murder of Candra Alston (25) and her daughter Malaysia (3) in 2011. Candra died from a shot in the head, and her daughter from multiple stab wounds. There were no witnesses, and the evidence that could be recovered came from a partial bloody handprint. 

The police at the time interviewed over 200 people and took DNA samples from 150, but they could not find any evidence to charge anyone. In 2015, DNA phenotyping was suggested.

The scientists were able to reverse-engineer the DNA found in the bloody print into an image of the suspect. According to Parabon, who developed the Snapshot^TM DNA Phenotyping System used, it can exclude physical traits with up to 95 percent accuracy and can predict pigmentation traits with an average accuracy of more than 80 percent.

The person of interest was described as having dark skin, brown hair, and brown eyes. A digital sketch made up of the data was released, and eventually, in 2017, this led to the arrest and conviction of Candra and Malaysia’s killer – Kenneth Canzater Junior. 

DNA phenotyping can also help identify victims 

There have been a few cases where DNA phenotyping was used for the identification of human remains. This has been useful in cold cases. For example, in 1985, a victim was found in a trash can and had suffered severe upper-body trauma. 

For many years, this victim was unknown. However, in 2016, police released a composite that was created using both forensic facial reconstruction and DNA phenotyping. Authorities were able to identify the body in 2019 as belonging to Roger Kelso, who was born in 1943 in Fort Wayne, Indiana, and is predicted to have died in 1963. 

DNA phenotyping has also been used in conjunction with genetic genealogy. In 2020, in a wooded area in Oregon, the remains of a partially skeletonized human female body were discovered. There were no strong leads in this case, so the Linn County Sheriff’s office decided to use DNA phenotyping and investigative genetic genealogy. 

The phenotype report revealed that the woman was of North European and African descent, had green or hazel eyes, light brown hair, fair skin, and potentially some freckling. The genetic genealogy report was able to provide a strong investigative lead: Grace Lorna Narvaez-Weaver, and the team were able to match this with the phenotype report.    

The future of DNA phenotyping

There have been a few developments in the accuracy of the technique over the years. At the beginning, it was mainly eye, (limited) skin, and hair color prediction that were used. Now, skin color is more established, and more DNA markers have been found, including: freckles, eyebrow color, hair structure, hair loss in men, gray hair, and tall stature.   

There has been an increase in research trying to predict age from crime scene DNA. One of these methods involves using DNA methylation-based age estimation tools. However, early research has shown that the older the person is, the less accurate it is. This is to do with the decreased DNA methylation stability when you are older. 

DNA phenotyping is still finding its forensic feet, and practitioners must tread carefully to overcome the issues associated with it, but it's already leaving impressive footprints. From helping catch murderers to identifying long-lost victims, it’s becoming a powerful addition to the forensic toolkit.