Investigating the crime scene

1. Identifying and Collecting Physical Evidence Investigating the crime scene

2. ONCE A CRIME HAS BEEN COMMITTED, THEN WHAT? • The location where a crime takes place is called a CRIME SCENE; • On arriving at the crime scene, police officers have 3 tasks to perform: • Call an ambulance and assist the injured at the scene. • Call in reinforcements. • Search the crime scene even if witnesses have indicated that the suspects have left.

3. Protecting and Preserving the Crime Scene (Securing the Scene)

4. PROTECTING AND PRESERVING THE CRIME SCENE • Police officers need to preserve and protect the crime scene from accidental or intentional contamination by anyone. • Crime scenes are preserved for 3 reasons: • To allow for a thorough search of the scene; • To seize and collect physical evidence; • To ensure that the physical evidence seized is not contaminated. • CONTAMINATION – is the loss, destruction, or alteration of physical evidence found at the crime scene. • If evidence becomes contaminated, it may be deemed inadmissible in court.

5. Four types of officers investigate the crime scene: • PATROL OFFICER • The first to arrive at the scene; • Primary duty is to secure the crime scene so evidence is not lost or tampered with; • Conduct initial interviews with witnesses of the crime; • Arrest suspects if they witness a crime in progress; • Determine the boundaries of the crime scene; • There are 2 boundaries established: • The CENTRE – where the offence was actually committed. • The PERIMETER – the areas surrounding the centre, where the offender might have been or left evidence

6. CRIMINAL INVESTIGATIONS BUREAU OFFICER • Plainclothes detective with experience in a particular area of crime, i.e. Homicide; • Supervise the investigation, interview victims and witnesses, interrogate suspects, draw conclusions from the physical evidence collected, and arrest suspects. • CRIMINAL IDENTIFICATION OFFICER • Search the crime scene for physical evidence; • Gather and analyze evidence; • Send evidence to the lab for analysis; • Tend to work on the more serious offences

7. SCENES OF CRIME OFFICER • Trained in evidence collection and preservation techniques – they must label all items, ensuring the evidence has not be contaminated or tampered with. • Usually skilled photographers; • Trained in lifting fingerprints and foot and tire impressions; • Collect blood and hair evidence; • Tend to work on less serious offences, i.e. Break and enter. • Police officers who are at the crime scene also keep a POLICE LOG, a written record of what the officer saw and learned from questioning suspects, to help preserve and protect evidence. • A CHAIN OF CUSTODY must be established for any evidence collected • This is a witnessed, written record of all the people who had control of the evidence; • Must remain UNBROKEN from the time the evidence is discovered at that crime scene until the time it is produced in court.

9. Examining the Scene • There are several search patterns available for a CSI to choose from to assure complete coverage and the most efficient use of resources. These patterns may include:

10. The inward spiral search: • The CSI starts at the perimeter of the scene and works toward the center. Spiral patterns are a good method to use when there is only one CSI at the scene.

11. The outward spiral search: • The CSI starts at the center of scene (or at the body) and works outward.

12. The parallel search: • All of the members of the CSI team form a line. They walk in a straight line, at the same speed, from one end of crime scene to the other.

13. The grid search: • A grid search is simply two parallel searches, offset by 90 degrees, performed one after the other.

14. The zone search: • In a zone search, the CSI in charge divides the crime scene into sectors, and each team member takes one sector. Team members may then switch sectors and search again to ensure complete coverage.

15. EVIDENCE AT THE CRIME SCENE • Crime scene investigation is carried out by officers who are trained in the analysis of physical evidence. They must: • Prepare a description of what they find; • Photograph the scene; • Prepare diagrams or sketches; • Collect evidence • Once the crime scene has been secured, the focus of the investigation is the collection of physical evidence; • When the evidence is brought back to the lab for analysis, it is examined by FORENSIC SCIENTISTS.

16. WHAT IS FORENSIC SCIENCE? • FORENSIC SCIENCE is the use of biochemical and other scientific techniques to analyze evidence in a criminal investigation • Forensic scientists include: • Pathologists (medical doctors who perform autopsies to determine time and cause of death) • Entomologists (those who study insects); • Firearms specialists; • Chemists • anthropologists

17. EVIDENCE FOUND AT THE CRIME SCENE – Direct vs. Circumstantial • Direct Evidence • Directly links the accused to the crime • Very hard to dispute • Video evidence, DNA evidence, some witness testimony • Circumstantial Evidence • Indirectly links the accused to the crime; • Gives an idea about what MIGHT have happened • For example, fibres, paint chips, some witness testimony

18. Physical Evidence • Physical evidence is the type of evidence collected at the crime scene. It includes: • Any object, impression, or body element that can be used to prove or disprove facts relating to an offence; • Physical evidence includes things left at the scene of the crime, such as a knife, fingerprints, gunshot residue, blood, and DNA evidence; • It often carries greater weight in court than evidence obtained through witness statements.

19. PHYSICAL EVIDENCE - TRACE ELEMENTS • i.e. dirt, dust, and residue, hair and fibres; • Though they may not prove a specific individual committed a crime, trace elements can link a suspect to a crime

20. TRACE ELEMENTS

21. Types of Physical Evidence – Body Elements and DNA • Includes blood, semen, mucus, sputum, hair, and skin; • Used to match with the DNA of a suspect; • Blood is the most common; • Hair and fibres are used to compare with those found from a suspect’s belongings; • DNA is different for each person, with the exception of identical twins; • The DNA of every cell in a person’s body is identical, but the pattern is different (except for identical twins): • The DNA profile of a suspect can be compared with the DNA profile found at a crime scene. If they match, they are from the same person; if they don’t, then the investigators need to find another suspect. • DNA is used to either link suspects to a crime with physical evidence, or free them from suspicion.

22. DNA

23. BLOOD SPATTER

24. Blood Splatter Analysis

25. MORE BLOOD SPATTER...

26. Collecting Physical Evidence • Objects, such as fingers, gloves, shoes, tires, and tools, leave impressions (patterns or marks) on various surfaces; • Impressions are collected by officers at the crime scene: • First, the impression is photographed, scanned, or a mould is taken, • The police then attempt to match the impression with the object that made it, i.e. The fingerprint to the person’s finger who made it.

27. Impressions • Impressions have 2 characteristics: class characteristics and individual characteristics. • CLASS CHARACTERISTICS – the general attributes of an object, such as type, make, model, style, and size (i.e. 12 inch steel belted radial, manufactured in 2005 by B. F. Goodrich Company); • INDIVIDUAL CHARACTERISTICS – the specific and unique features of an object, such as a particular indentation on the head of a hammer, or the amount of wear on a tire.

28. Types of Physical Evidence that leave Impressions - Tools • Most frequently used are hammers, screwdrivers, and crowbars; • Markings can be analyzed in the lab and matched with wounds found on the victim

30. Types of Physical Evidence that leave Impressions – Shoe Prints and Tire Tracks • Shoe prints help to determine the height and weight of a suspect, as well as any injuries they might have sustained committing the crime, or whether they were carrying anything, walking, or running. • Tire impression can help determine the type of tires, the make of car, and the direction the car was going

33. Types of Physical Evidence that leave Impressions - Gloves • Glove impressions can be used to identify a suspect in almost the same way fingerprints are: • The class characteristics (the overall pattern of the glove and the spacing of its stitches) and individual characteristics (worn or torn areas), are compared with the gloves of a suspect.

34. Types of Physical Evidence that leave Impressions - Fingerprints • The mark left behind by a fingertip; • Prints can be taken from a person’s hands, feet, or toes, but fingerprints are the easiest to work with and classify; • Fingerprint patterns never change and are unique to each individual – no 2 people have the same fingerprint pattern; • Are the best type of impression to use to identify an offender

36. Fingerprints continued • There are 2 types of fingerprints: • VISIBLE FINGERPRINT – a print that can be observed by the naked eye because it is coated in blood, dirt, grease, or some other substance; • Can be photographed immediately. • LATENT FINGERPRINT – a print that is made by the perspiration and oils that naturally form on the skin surface and cannot be seen by the naked eye; • Must be developed before they can be photographed: • Dusted and then lifted when on non-absorbent surfaces like metal or plastic; • Iodine fuming is used for absorbent surfaces, such as paper and cloth; • A laser beam can be used to illuminate the print – the sweat absorbs the laser and turns the print yellow, allowing it to be photographed.

38. Types of Fingerprint Patterns • All patterns are one of 3 main types: • Arches – form ridges that run from one side of the print to the other and curve up the middle; • Loops – showing stronger curves than arches with ends that start on one side of the finger, loop around, and end up in the same place; • Whorls – forming complete ovals, often in a spiral pattern around a central point.

39. Types of Fingerprint Patterns

40. FINGERPRINT PROCESSING • In Canada, fingerprints taken from a crime scene are sent to a central repository administered by the RCMP in Ottawa; • Identity is determined by comparison – 10 to 12 points must be identical for an expert to form the opinion that the print submitted is that of an individual whose prints are on file.

42. Let’s Try it Out! • On your desks, you have probably noticed a few items: ink pad, recipe card, brushes, magnifying lens, fingerprinting powder, clear tape, wipes, and a variety of other items (plates, mugs, etc.). • The ink pad and recipe card are there for you to take your own fingerprint and determine what type it is. • The rest of the items are for you to practice lifting fingerprints off the different items. • Refer to the instructions provided for how to complete each of these activities.