Third in a three-part series
Ever since the 1990s, when DNA testing was introduced in this province as a means of fighting crime, it has been integral in solving high-profile cases.
One of the first was the 1996 murder case of Nina Walsh, who was killed in her Avalon Street home in St. John's.
Walsh had been stabbed in the back of the neck and was found lying on the floor with her shirt pulled up. The words "You're next" were written across her chest in ketchup.
From DNA samples collected at the scene and from suspects, investigators determined that Eric Squires was the murderer. When Squires was searched, officers found Walsh's DNA on him.
"It was a faint amount of blood," said Sgt. Karl Piercey, a forensics supervisor with the Royal Newfoundland Constabulary in St. John's.
"So faint, you could hardly tell it was blood."
Then there was the 1998 case of Catherine Clowe, a 78-year-old woman who was strangled to death with a telephone cord in her house on Pennywell Road.
Clowe's granddaughter, Krista Constantine, and her then-boyfriend Fred Noftall were arrested after investigators found a denim shirt of Noftall's - with a relatively fresh bloodstain - in Constantine's house.
"This was a jean shirt and the deceased's DNA was around the stomach area," Piercey said.
Constantine was convicted of second-degree murder, while Noftall was found guilty of manslaughter and sent to prison for a year. He had been in prison for three years before his trial.
Freeing the innocent
DNA testing has also led to the exoneration of people previously convicted of crimes.
In one of the most publicized cases in this province's criminal history, Gregory Parsons was convicted of the murder of his mother.
Parsons was cleared by DNA evidence in 1998, four years before, Brian Doyle, his childhood friend, pleaded guilty to the crime and is serving a life sentence.
Parsons' wrongful conviction, and others, led to the Lamer Inquiry, which resulted in the police implementing stricter standards and procedures in crime-scene investigations.
Human fingertips have friction ridges, which create the individual print.
They're so unique to each individual that thumbprints are often used as signatures.
Fingerprinting is performed by dusting a specially formulated powder onto surfaces to determine who has been at the scene. The powder must be fine to adhere to the impression of the fingerprint. The fingerprinting brush, in turn, must have fine fibres to hold the powder without erasing the fingerprint.
"It's a carbon-based powder," Piercey said. "If you were crush up some cigarette ashes, you'd almost have the same thing."
The powder adheres to moisture, which is secreted as perspiration, he explained.
"Everyone sweats," he said. "When you touch something, that moisture comes off."
Once the powder is dusted on, a clear adhesive - much like tape - is used to lift the impression off. It's then placed against a contrasting coloured background for examination.
"We'll do a visual examination to see if it's suitable to be searched and compare it to suspects here," he said.
"If we don't get a match, we'll ask the investigator to provide elimination prints from owners and people in the house, so we can eliminate them as being the source of the print."
The print is then photographed or scanned and sent to Ottawa, where a national database is searched.
Footprints can also be lifted using powder brushing.
However, to recover larger, sunken impressions left in muddy conditions, investigators have to make casts.
Much the way a dentist creates a mould of a patient's teeth, officers use products to make an impressions of footprints in order to examine the tread of the person's footwear. The same method is used with tire marks.
Chemistry can also play a role in discovering evidence, and one of the most important chemicals is Luminol.
Used here since the 1970s as a standard forensics technique, Luminol can detect traces of diluted blood that would not be seen by the naked eye.
When sprayed on surfaces, it reacts with the iron found in hemoglobin and creates a chemical reaction - blood-spatters will emit a blue glow.
"But when you use the chemicals, that's one of the last searches," Piercey added, "because you're spraying a liquid that will most likely destroy anything else that's there. But the guys on the scene are cognitive of that."
Luminol was used to solve the grisly 2008 murder of Amanda Power, who was strangled to death in her Warbury Street apartment in St. John's and her body dismembered.
Investigators sprayed Luminol in the bathtub of the home she had shared with her boyfriend, Warren White. The tub looked clean to the naked eye, but the chemical revealed blood-spatters.
It was later determined that White had cut Power's body into pieces in the tub before disposing of the parts in a suitcase and other bags.
White was convicted of second-degree murder and sentenced to 17 years in jail.
Booze and your breath
Chemistry also plays a role in convicting drunk-drivers.
When motorists believed to be impaired are stopped by police, they are asked to breathe into a device.
The breathalyzer gives a chemical analysis of the level of alcohol on someone's breath.
The breath sample is bubbled in a vial through a mixture of sulfuric acid, potassium dichromate, silver nitrate and water. That creates a chemical reaction that can be detected when it reacts to the alcohol in the breath sample.
Other scientific tools
Crime scene investigators are not limited to particular scientific fields in fighting crime.
"We use everything we can apply to help us," said Piercey, who said officers often call on outside sources, such as professional scientists, to help in an investigation.
"Forensics, itself, is a science because it takes little bits and pieces from every other scientific discipline and uses it to prove fact."
Police often use entomology and botany to determine the timeline of a crime.
For example, if a body is discovered in the woods, investigators can look at insect activity and insect lifecycles and the rate of decomposition to determine how long the body has been there. Investigators can study plant life around the body to answer the same question.
There's ballistics, which involves the projectiles of bullets, and odentology, which can be used to examine bite marks and other dental evidence.
"Forensic odentology has emerged as one of the most important offshoots of forensic medicine," says the Internet Journal of Forensic Science. "It has proved to be invaluable in criminal investigations of different types including rape, child abuse and murder. Bite mark analysis is a vital area within this highly specialized field and constitutes the commonest form of dental evidence presented in criminal court."
Toxicology - the effect of chemicals on the human body - is also useful in pinpointing people's physical state at the time of a crime.
Toxicology reports from victims and accused persons are commonly used in trials.
Far from glamorous
Crime scene investigation is painstaking work which requires careful analysis and patience.
Piercey said it differs vastly from the way it's portrayed on TV crime shows, where investigators deal with witnesses and suspects and solve crimes in the span of a few days.
"It's all embellished and sensationalized," he said. "The timeframes are way out of whack. … It often takes a long time, and a lot of hard work, to solve a crime."
The RNC has expanded its forensic unit in recent years to keep on top of trends that are being seen right across the country.
"Lately, in the courts, eye-witness evidence is being detracted from and scientific evidence is given more weight," Piercey said, "so you have to dedicate your resources where it's going to be the most effective."
The satisfaction comes when the marriage of science and justice produces a resolution.
"Finding that smoking gun at a crime scene, it's just a real high sense of personal accomplishment," Piercey said.
"Science plays a big part in identifying suspects, and when that happens, it's a feeling like you wouldn't believe."