New blood test set to help murder detectives

It’s a stalwart part of police procedural novels and television shows, not to mention real investigations.

The cops get called to a crime scene: there’s blood and gore everywhere, but no body. It’s reasonable to deduce that someone has come to a nasty end, but who? Forensic examiners descend, scraping up bits of every fluid they can find and taking it back to the lab for analysis.

The standard battery of crime scene tests can produce very useful information, but, in the end, each has its limitations. One important aspect that existing techniques can’t shed any light on, for instance, is the chronological age of an unknown and missing victim.

That may all be about to change, thanks to research completed by chemists Kyle Doty and Igor Lednev from the State University of New York in the US.

In a paper published in the journal ACS Central Science, the pair reveal a new simple test that be conducted in the field and which will reveal the rough age of a missing victim.

The test utilises a method known as Raman spectroscopy, a non-destructive approach which exploits the relationship between electromagnetic radiation and matter. The technique uses a laser beam that interacts with vibrations within a molecular system – in this case, haemoglobin – which shifts the energy value of the laser’s phonons up or down.

To make their findings, the scientists tested blood taken from 45 volunteers, including newborns, adolescents and adults. The blood was rendered as stains – in a touch of crime scene verisimilitude – and first subjected a test known as support vector machines discriminant analysis (SVMDA) to provide independent confirmation that it was, indeed, blood and not some other kind of gross murder-linked bodily fluid.

This done, Doty and Lednev applied Raman spectroscopy to markers with haemolglobin molecules. Identifying the newborns was quite easy because baby blood contains a foetal version of the substance (known as HbF), which is structurally distinct from the adult version (known as HbA).

By measuring the comparative peaks and troughs of the spectroscopic vibrations in the blood samples, the researchers were able to identify newborn “victims” with 100% accuracy, and recorded rates above 90% for adolescents between 11 and 13 years old, and adults between 43 and 68 years old.

(The age groupings reflect the real ages of the volunteers rather than any kind of weird cut-off points emerging from the method.)

The researchers describe their results as merely proof-of-concept at this stage, and acknowledge the need for more widespread testing. However, they note, if further work confirms their findings across a wider pool of volunteers, the test could provide detectives with valuable leads in a short period of time while at the same time preserving the specimen for evidentiary use or later tests.

“This approach could provide significant benefits to advancing the field of forensic science, specifically serology, to help narrow down a suspect pool or help determine the age of a victim,” they conclude.