How do police forensic scientists investigate a case?
A clandestine gravesite recovery expert Brendan Chapman explains more
Perth: Recent high-profile missing persons cases, including that of William Tyrrell – who went missing in Kendall, New South Wales, at the age of three in 2014 – have focused public attention on the forensic practices involved in crime scene investigations. As a forensic scientist who has worked at thousands of homicide, sexual assault and serious crime scenes, Brendan Chapman, from Murdoch University, can tell us this process is not as straightforward as depicted on popular true crime shows.
“I research and teach forensic science at Murdoch University and specialise in cold-case techniques and clandestine gravesite recovery. Here’s what typically happens behind the lines of police tape when forensic teams are at work.
In the first moments after a major crime, what has happened is often a mystery. Like a scene from a painting, it’s as if time stood still; many regular household items sit as they did before the violent event took place. Investigators take great care not to disturb the initial scene, lest valuable evidence be lost. The first task is to record everything as it appears in incredible detail — by video, photo and in written notes. Even items that may first appear innocuous can later take on new significance. This stage is vital; years later, this may be the only way cold-case teams can virtually revisit the scene to identify new clues.
As the forensic investigation unfolds, information and evidence are gathered and given to investigators at the crime scene. This helps provide context to guide the search for evidence.
The crime scene team works meticulously to identify and “field-test” items before securing them in bags. In some cases, that’s by using chemicals and testing kits to identify body fluids or other traces associated with the crime.
We also use some very high-tech torches that can emit a specific type to light to help us see otherwise invisible clues. This works a bit like the lighting in nightclubs that might expose lint on your black outfit.
At this stage, the best crime scene examiners invoke the scientific method, proposing hypotheses as to what has happened, and then searching for evidence that may refute their suggestion.
Other specialised forensic practitioners include pathologists, insect experts, anthropologists, biologists and chemists.Forensic investigations are most successful with a multidisciplinary team, which allows for many different opinions and ideas.