Your DNA is everywhere: your blood, hair, skin, and in every drop of bodily fluid.
That might seem gross, but it’s an inescapable fact – your genetic material is being left behind, wherever you go.
That’s useful for forensic scientists who survey crime scenes to understand what happened, how, and to whom, as the latest episode of Demystifying Forensics on The Science Briefing explores.
One of Australia’s top forensic pathologists is Roger Byard. Over a decades-long career being appointed to major cases across Australia and the world, he has notably worked on identifying remains in the Bali Bombings, Thailand tsunami tragedies, and notorious Snowtown murders.
Byard says the process, whether a high-profile, or smaller, localised crime scene, is the same in principle: work with law enforcement to analyse the incident and avoid contamination of the evidence.
“Particular instruments or materials are significant. If there are blood spatters around the crime scene, officers will sample those for DNA because that may be the blood from the deceased, but it may also be the blood from the perpetrator,” Byard tells Cosmos.
But while the principles are simple, the process is not necessarily straightforward.
Co-mingled remains complicate matters in the event of catastrophic events like an explosion, and although on-scene or laboratory contamination is avoided wherever possible, it can muddy the situation.
Even the occasional chance that an innocent bystander interacts with the crime scene can obscure the true nature of events.
That is the challenge that faces forensic pathologists. When arriving at the scene, they’ll engage with police to, in Byard’s words “bounce ideas” that try to make sense of the circumstances they’ve encountered.
Providing investigators with the best possible assessment of a crime scene is crucial to the pathologist’s role. That’s the reward pathologists draw from encountering often tragic scenes every day.
“It can be a violent scene, it can be a very confusing scene – you just don’t know what has happened to start with,” Byard says.
“But I think the process of logically going through [the scene] is really, very satisfying.”
To understand how expert forensics unscramble the genetics uncovered at a crime scene, and some of the cases that have been cracked open by DNA, check out the latest episode of The Science Briefing with Dr Sophie Calabretto and Matthew Agius.