It would cut short a good crime novel if forensic investigators had the tools to determine the appearance of an offender from the cellular material contained in blood stains at a crime scene. However, the forensic science community is developing analytical tests that could distinguish ethnicity, eye colour and, now, age.
Some of the most recent research uses a component present in a group of white blood cells, T‑lymphocytes. As a function of age, there is a decline in the number of these components within the cells. In a study of 195 individuals, the researchers predicted the ages of the subjects to within 9 years of their actual age. Ideally, this would enable investigators to narrow down a suspect pool when other methods, such as comparing DNA profiles to a database, have failed to otherwise identify the donor of the blood stain.
Being able to determine a person’s age to within 9 years may sound super-whizzy and significant. However, Statistics New Zealand’s Crime Statistics for 2010 indicate that the majority of people committing crimes were within 17 to 30 years old. The new test is therefore unlikely to be able to distinguish a large proportion of this group and may fall short in actual casework application. It could be an interesting tool for intelligence purposes though, but could not be used to identify an individual – and with budgets being the key to everything, forensic laboratories might not invest in technology that gives such limited intelligence.
Using a DNA profile to determine ethnicity already has its problems: people do not look as they should. A DNA profile may identify someone of Asian descent but, depending on parentage over the years, the person may not have a traditional Asian appearance. Similarly, using features within a cell to determine a person’s age has the same fundamental problem. The T-cell component from the crime scene blood stain may identify a 30 year old as being the donor but the years can be kind or harsh for different individuals exposed to different conditions and they may not look their age; indeed, the age-determining researchers point out that blood from people with immunosuppressant diseases may appear ‘older’ than they are. Aside from disease and medical disorders, there’s a whole industry dedicated to not looking one’s age: the beauty industry. In woman’s magazines weekly diet, fish oil, botox and a variety of other products designed to separate women (and men) from their cash are prescribed as the key to altering appearance.
Although this research may be a huge development for science and for research into ageing, its application to forensic science at the moment may be limited. The future is a different matter.
Plus, it’ll make a good storyline on Bones…
Zubakov, D. et al. 2010. Estimating human age from T-cell DNA rearrangements. Current Biology 20 (22)
Liu, F., et al. 2009. Eye color and the prediction of complex phenotypes from genotypes. Current Biology 19(5)
by Paige Eyton, Consultant Forensic Scientist (first in NZLawyer Magazine April 2011)