A blood-stained cloth was the only evidence police had to work with when Marlene Maria Smith didn’t turn up to work in August, 2000.
This small clue would soon become part of the huge web of forensic evidence.
Forensic investigator Peter Baines used glowing chemicals to detect the presence of blood in Smith’s New South Wales home.
Crime scene investigator Peter Baines discusses the case on the Crime Insiders podcast:
There are two types of chemicals forensic investigators use to reveal the presence of blood at a crime scene.
Baines said luminol is used first, which glows when it reacts with the hemoglobin in blood.
“It’s an agent which is mixed. And then put in a spray bottle and it’s sprayed on the scene. And you’ll get a chemiluminescence,” he said.
Luminol fades quickly, meaning investigators need to be ready with their cameras to record it so images can be presented as evidence in court.
After luminol revealed the presence of blood, Baines employed leucocrystal violet (LCV) to produce a permanent, clearer image of the blood stains.
Unlike luminol, LCV doesn’t require darkness to glow.
“What was revealed by the presence of the LCV was these very clear marks on the wall, which were an indication of a wet cloth with these sideways marks where someone’s cleaned something up.”
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