Canadian Policing and Forensic Sciences Quiz

Protecting a Crime Scene and Collecting Evidence

• A crime scene is the location where a crime occurred.
• Protecting a crime scene involves establishing boundaries (center and perimeter) to prevent contamination.
• This protection allows for a thorough search of the scene and ensures collected evidence is admissible in court.
• Officers will call an ambulance and assist injured people at the scene, call reinforcements to eliminate hazards.
• Officers must continue to search the crime scene even if witnesses say that suspects have left.

Canada's Police Forces

• Canada's police forces cost approximately 16 billion dollars in 2019.
• There are over 66,000 officers at three levels (federal, provincial, and municipal).
• The Royal Canadian Mounted Police (RCMP) was formed in 1873.
• The RCMP is the federal police force in the territories.
• The RCMP also serves as provincial police in all provinces and territories except Ontario, Quebec, and Newfoundland and Labrador; however, they can also serve as municipal police.
• The RCMP is responsible for all federal law under the Criminal Code.
• Their responsibilities include Border Integrity, Drugs and Organized Crime, International Policing, and Financial Crime.
• Provincial police forces include the Ontario Provincial Police (OPP) as the largest force.
• Municipal police have jurisdiction solely in their specific towns and cities.

Investigating a Crime Scene

• Four types of police officers investigate a crime scene:
  • Patrol officer—has a beat and regularly checks the area; the first to arrive; secures scene with yellow tape.
  • Scene of crime officer—trained in evidence collection and preservation techniques.
  • Criminal identification officer—searches, examines, collects physical evidence, and sends relevant evidence to a lab.
  • Criminal investigations bureau officer—a plainclothes detective with specialized experience.

Arriving on the Scene

• A police officer's role upon arriving at a scene includes:
  • Assist the injured
  • Call for reinforcements to eliminate hazards.
  • Search for perpetrators.
  • Secure the scene: establishing the center of the crime scene and a perimeter.
  • Avoid contamination and create a police log.

Evidence Contamination

• Evidence can be contaminated if mishandled.
• Contamination involves loss, destruction, or alteration of physical evidence.
• Officers must protect and preserve evidence.
• A police log (written record of an officer's observations) helps recall events, especially for trial testimony.

Crime Scene Recording

• Recording involves:
  • Exact measurements
  • Photographs
  • Labelling of evidence

Physical Evidence

• Physical evidence includes any object, impression, or body element used to prove or disprove facts related to an offence.
• It is more important than witness statements.
• Forensic science uses biochemical and other scientific techniques to analyze evidence.
• A pathologist performs autopsies to determine how and when a person died.
• Scientists specialize in firearms analysis to identify the type of gun used in a crime.

DNA Testing

• DNA testing has only been used in criminal investigations for the past 20 years.
• The technology has improved significantly.
• The most common sample used is blood, along with hair shafts, mucus, skin, saliva, and semen.
• DNA testing is still slow and expensive.
• It is often used to affirm that a suspect is the perpetrator.

Blood Spatter and Typing

• Blood spatter patterns reveal details about the crime, like whether an artery was severed, if the person was bludgeoned, stabbed, or had their neck sliced open.
• Scientists use trigonometry and calculus to determine the perpetrator's height.

Gunshot Residue

• When a gun is fired, minute amounts of explosive primer, propellant, and metal cartridge particles are sprayed onto the individual holding the gun.
• Two types of gunshot residue (GSR) tests exist:
  • Modified Griess test for clothing (nitrate residue).
  • Sodium Rhodizonate test (lead residue—turns pink then blue).
  • Distance Determination Analysis—calculates factors related to gunshot distance.

Angle of Gunshots

• The angle of a gunshot can indicate where and how tall the shooter was.
• Technicians use laser sights, rulers, and dowels to determine the bullets' trajectory, to possibly rule out a suspect or identify someone as the shooter.

Caliber Testing

• Caliber testing matches markings on bullets and casings with the corresponding gun to determine if it was the murder weapon.
• Testing involves firing a gun into a testing chamber, retrieving the bullet, and matching the grooves.

Stab Patterns/Wound Patterns

• Every tool (including weapons) leaves behind markings and impressions, especially with weapons like serrated knives that can leave jagged wounds.
• Wound patterns are photographed, and sometimes castings are made for later comparisons with possible weapons.

Tire Treads

• Tire treads left in dirt, mud, or snow on a crime scene provide information such as the car's make, model, wear condition, and the load it was carrying.
• Three types of tire prints exist:
  • Visible: seen by the naked eye.
  • 3D: impression made from plastic or plaster.
  • Latent: not seen by the naked eye made from static electricity.
• Technicians measure, photograph, and create models of the prints to identify unique characteristics, which are then compared to known tires.

Markings

• Markings (for example, from tools or weapons) on a surface indicate what was used (and possible perpetrators).
• Markings can be compared to possible weapons (wire cutters, crowbars, etc.) to potentially determine the perpetrator.

Fibers

• Fibers transferred between clothing or objects (even from carpet) can be used as clues at a crime scene.
• Fiber samples are collected to determine their composition and origin.
• If the suspect has access to items with those same fibers, it may indicate they were at the crime scene.

Sexual Assault Kits

• A series of tests conducted at facilities (clinics, hospitals, doctors offices) to collect evidence.
• Commonly referred to as rape kits, SAFE kits, or PERK kits.
• Evidence collected includes photographs, swabs, DNA samples, fingernail scrapings, clothing, and other physical evidence.

Fingerprints

• Two types of fingerprints exist:
  • Visible: seen by the naked eye (in dirt, oil, or blood).
  • Latent: not easily seen by the naked eye (require special techniques to make visible).
• Visible and latent fingerprints can give investigators critical information.

Plants/Animals

• Like fibers, plant and animal matter can transfer between people, and people to the crime scene.
• Identifying samples from these materials (hair, plant tissue) can narrow the pool of suspects.

Footprints

• Footprints (visible or latent) can be measured; photographed; or impressions made of them.
• Footprints provide information like height, weight, how the person walks.
• Latent prints can be made visible by dust using electrostatic powder.

Autopsy

• A full examination of the inside and outside of a body to determine the cause of death and identify possible evidence.
• A medical examiner or pathologist conducts autopsies.
• During an autopsy, the exterior of the body is photographed, hair combed, fingernails scraped; a Y-incision is made.
• Organs are weighed and tested for toxins.
• Injuries and bullets are examined and documented..
• Bullets are sent to ballistics for further testing.

Examples of Physical Evidence

• A chart showing various examples of physical evidence, categorized as objects, body materials, and impressions.

Real Life CSI

• Brief discussion of CSI in real life and a link to further related information.

Forensics and Impressions

• Brief Discussion of Forensics and Impressions with links to additional resources.

Great Forensics Website

• An online resource providing a simplified guide to forensic science, with various topics.