Starting a Police Investigation

1. Starting a Police Investigation

2. The “Crime Scene” • Arriving at a “Crime Scene”—the location where an offense takes place is referred to as the crime scene.

3. What to do first? • When officers arrive they have three tasks to perform: • Assist injured people/call an ambulance • Call in reinforcements to eliminate hazards (bombs, fires etc.) • Continue to search the crime scene—even if they think perpetrators have left. ASSUME PERPETRATORS ARE PRESENT AND ARMED.

4. Protecting and Preserving the Crime Scene Protecting and Preserving the Crime Scene—success in prosecuting a case often depends on the evidence collected. Officers must establish two boundaries—the centre (where the offense was committed) and the perimeter (surrounding areas where evidence may be present)

5. Crime scenes are preserved for three reasons: allow for search, seize and collect evidence and ensure evidence is not contaminated (loss, destruction or alteration of physical evidence)

6. Officers at the Crime Scene • Officers role at a crime scene—Four types of officers investigate at a crime: • Scenes of Crime Officer • Criminal Identification Officer • Criminal Investigations Bureau Officer • Patrol Officer

7. Scenes of Crime Officer—trained in evidence collection/preservation • Criminal Identification Officer—resp. for searching the crime scene for evidence

8. Criminal Investigations Bureau Officer—detective with experience in specific area (homicide, robbery, sexual offences) • Patrol Officer—usually first on the scene. Must secure crime scene/arrest suspects.

9. Physical Evidence • Collection, preservation and analysis of evidence is crucial • Physical evidence is defined as: any object, impression or body element that can be used to prove or disprove facts relating to an offense • Valuable because it often carried greater weight in court than witness statements

10. Forensic Science • The use of biochemical and other scientific techniques to analyze evidence in a criminal investigation • Work done mostly in the lab but experts also testify in court • Examples: autopsy, firearms/ballistics, forensic chemists, etc

11. Tools • The tools used in the commission of a crime leave an imprint behind • May have individual characteristics • Most common: hammer, screwdriver, crowbar

12. Impressions • Patterns or marks found on surfaces and caused by various objects • Fingers, gloves, shoes, tires, tools etc • Impression recorded by photographing/scanning it or taking a mould • Two characteristics: • Class characteristics: general attributes • Individual characteristics: specific to that object

13. Fingerprints • Patterned marks left by a fingertip (also hands, feet, toes) • Unique and never change • Visible fingerprint: print formed in blood, grease or some other substance—seen by the naked eye • Latent fingerprint—formed by natural oils and perspiration. Invisible to the naked eye • Fingerprints can sometimes be left INSIDE gloves

14. Shoe prints • Can be matched to suspect • Best if they have four prints—two of each foot • Can determine height, weight, injuries, whether the suspect was carrying anything, walking or running

15. Tires tracks • Can determine the make of tire • make of car (sometimes) • the direction the car was travelling when it entered/left the crime scene

16. Body elements and DNA • Crimes often result in the transfer of bodily fluids • Blood, semen, mucus, sputum, hair, skin • Sent for laboratory analysis • Analyzed for a match to the suspect • Hair and fibres may also be matched

17. Chain of custody • Proper labelling is important • Who has contact with the evidence • The date and time the evidence was handled • The circumstances under which the evidence was handled • What changes, if any, were made to the evidence

18. Information required: • Brief description • Police case number • Date collected • Location of collection • Brand name of item (if any) • Serial number • Name and badge number of officer who collected • Destination for storage or analysis