crime scene investigation

1
How Crime Scene Investigation Works
2
CSI Basics

• The goal of any investigation is to convict the
  perpetrator of the crime.
• Need to gather physical evidence without
  disturbing trace evidence
• Need to preserve evidence in current form
• Need to consider what the lab will need to do
  with the evidence
• Need to consider the legal issues of making
  evidence admissible in court.

3
Who is there

• Police
• CSI unit
• District attorney
• Medical examiner

4
Police on the scene

• Police are typically first to arrive
• Arrest the perpetrator if still on site
• Call for an ambulance if needed
• Secure the scene.

5
CSI Team

• Documents the scene and collects evidence

6
District Attorney

• If the investigators need a search warrant
• Obtains search warrants from judge

7
Medical Examiner

• In the case of a homicide
• Determine preliminary cause of death

8
Steps of a CSI investigation

• Call is made from the police or detectives on the
  scene to the CSI team to come investigate
• Police must be sure the scene has been secured
• No random people wandering and disturbing evidence

9
Initial walk-through

• CSI gets an overall feel for the crime scene
• Find out if anything has been moved
• Makes general initial theories
• Makes a note of potential evidence
• At this point - TOUCHES NOTHING!

10
Documents the Scene

• Taking photographs and making sketches during a
  second walk-through.
• Walk-through is often done with videotape
• CSI still touches NOTHING

11
Collect all potential evidence

• Tag log and package evidence to stay in tact
  until it reaches the lab
• CSI may or may not do any analysis of evidence
  depending upon their individual field.

12
Crime Lab

• Processes all evidence
• Lab results will go to the lead detective

13
Video clip

• http//science.howstuffworks.com/csi.htm

14
At the crime scene

• Scene recognition

15
Extent of crime scene

• Define the boundaries of the crime scene
• Example a homicide
• Victim the house area around house cars in the
  driveway blood trails could become quite large

16
Securing the crime scene

• Consider other areas that might be part of the
  crime scene
• CSI gets one chance to gather all possible
  evidence
• Evidence becomes corrupted

17
Core area

• Most obvious part of the crime scene where the
  most evidence is concentrated
• Usually secured by police
• CSI usually extends the area after walk-through
• Also contains a safe area to maintain the core
  area to decrease the potential for error

18
Search warrant

• CSI will obtain a search warrant
• Ensures the evidence will be admissible in court

19
Walk-through

• CSI takes immediate note of details that will
  change over time
• Weather
• Time
• Smells
• Sounds
• Smoke
• Also checks for potential hazards
• Gas leaks
• Fire
• Dogs
• Other suspects

20
Specialists

• CSIs do not talk to witnesses - that is the job
  of the detectives
• Call in specialists for individualized work
• Call in any specialized equipment

21
At the crime scene

• documentation

22
photos

• Creates a visual record used to recreate the
  scene and re-examine evidence
• Use digital cameras video cameras various lenses

23
Note-taking

• EXTREMELY detailed notes
• Include sketches and measurements

24
Clean up crews

• CSIs do not clean up the crime scene
• Left to the families
• Companies are now available to hire for crime
  scene clean up.

25
Video clip

• http//videos.howstuffworks.com/investigation-disc
  overy/14251-crime-scene-clean-up-steps-for-cleanin
  g-video.htm

26
At the crime scene

• Finding evidence

27
Types of evidence

• Trace evidence
• Impressions
• Body fluids
• Hair and fibers
• Weapons and firearms evidence
• Questioned documents

28
Trace evidence

• Gunshot residue
• Paint residue
• Broken glass
• Unknown chemicals
• Drugs
• Hair and fibers

29
impressions

• Fingerprints
• Footwear
• Tool marks
• Tire tracks

30
Body fluids

• Blood
• Semen
• Saliva
• vomit

31
Weapons and firearms

• Knives
• Guns
• Bullet holes
• Cartridge casings

32
Questioned documents

• Diaries
• Suicide note
• Phone books
• electronic documents
• Answering machines
• Caller ID
• Cell phones

33
Examining the body

• If there is a homicide the body must be examined
  first
• Body will be taken with the medical examiner for
  autopsy
• All evidence must be recovered from the body
  before it is moved

34
Before moving the body

• Are there stains or marks on the clothing
• Is the clothing bunched up in a particular
  direction
• Could indicate dragging from the original
  location
• Are there any bruises cuts or marks on the
  body
• Defensive wounds
• Are injuries consistent with the preliminary
  cause of death
• Is there anything obviously missing
• A tan mark from a watch or ring

35

• Is there blood present in large amounts
• Does the direction of flow follow the laws of
  gravity - body could have been moved
• If there is no blood present
• Is it consistent with the preliminary cause of
  death - body could have been moved
• Are there any bodily fluids besides blood
• Is there insect activity on the body
• Insect activity can determine time of death

36
The body is turned over

• Same sequence of examination is performed on the
  reverse side
• Body temperature and ambient room temperature is
  then taken
• Fingerprints are taken
• Either at the scene or at the MEs lab

37
Preparing for the Autopsy

• The hands and feet are bagged
• The body is wrapped in white cloth
• The body is transported to the morgue

38
Autopsy

• Body is examined for trace evidence
• Additional photos and video are taken
• Tissue samples are taken for further analysis

39
Examining the scene

• search patterns
• Inward spiral
• Outward spiral
• Parallel search
• Grid search
• Zone search

40
Inward Spiral Search
Used when there is one CSI present to look for
evidence
41
Outward spiral Search
Usual search pattern when the search starts at a
body
42
Parallel search pattern
Investigators walk in a parallel line at the same
pace across the crime scene
43
Grid search Pattern
Same as a parallel search only a second search is
done after the first at a 90 degree angle
44
Zone Search
CSI divides the crime scene into sectors and each
investigator takes a section then they switch
45

• Are the doors and windows locked or unlocked
  Open or shut Are there signs of forced entry
  such as tool marks or broken locks
• Is the house in good order If not does it look
  like there was a struggle or was the victim just
  messy
• Is there mail lying around Has it been opened
• Is the kitchen in good order Is there any
  partially eaten food Is the table set If so
  for how many people
• Are there signs of a party such as empty glasses
  or bottles or full ashtrays
• If there are full ashtrays what brands of
  cigarettes are present Are there any lipstick or
  teeth marks on the butts
• Is there anything that seems out of place A
  glass with lipstick marks in a mans apartment
  or the toilet seat up in a womans apartment Is
  there a couch blocking a doorway
• Is there trash in the trash cans Is there
  anything out of the ordinary in the trash Is the
  trash in the right chronological order according
  to dates on mail and other papers If not
  someone might have been looking for something in
  the victims trash.
• Do the clocks show the right time
• Are the bathroom towels wet Are the bathroom
  towels missing Are there any signs of a cleanup
  
• If the crime is a shooting how many shots were
  fired The CSI will try to locate the gun each
  bullet each shell casing and each bullet hole.
• If the crime is a stabbing is a knife obviously
  missing from victims kitchen If so the crime
  may not have been premeditated.
• Are there any shoe prints on tile wood or
  linoleum floors or in the area immediately
  outside the building
• Are there any tire marks in the driveway or in
  the area around the building
• Is there any blood splatter on floors walls or
  ceilings

46
Things to remember

• Crime scenes are three dimensional CSIs must
  always remember to look up
• A CSI must shine a light on the ground at various
  angles even if there is plenty of light the
  angles create shadows that can reveal evidence
• Always look for cigarette butts they are an
  easy source for DNA

47
Trace Evidence

• Gun-shot residue
• Paint residue
• Chemicals
• Glass
• drugs

48
Trace evidence collection

• Tweezers
• Plastic containers with lids
• Filtered vacuum device
• Knife
• Biohazard kid containing gloves booties face
  mask gown and biohazard waste bag

49
Crimes involving guns

• CSI collects clothing from the victim and anyone
  who may have been at the scene to test for gun
  shot residue
• CSI places all clothing into sealed paper bags
  for transport

50
Trace evidence room

• Much evidence can be found by shaking out
  bedding clothing towels couch cushions and
  other items

51
Body Fluids

• CSI can smear samples ontos for transport
  to the lab
• CSI can also use sterile cloth squares to gather
  fluid samples
• CSI can detect blood with luminol and a UV light

52
Evidence on the body

• Blood samples are collected with sterile cloth
  and distilled water
• Victims nails are scraped for skin
• Saliva and semen are also collected from the body

53
Blood Spatter patterns

• Can reveal the type of weapon used
• Can indicate which direction the blood came from
• CSI studies size shape and the size and shape
  of the blood droplets

54
Hair and Fibers

• CSI uses combs tweezers containers and a vacuum
  device.
• In the case of a live victim the CSI with travel
  to the hospital to recover hair and fibers during
  the medical examination
• Fibers can be recovered from shoes

55
Firearms

• All firearms bullets or casings found at a
  crime scene are collected and bagged
• Using a laser trajectory kit CSIs can determine
  from where and what height a bullet has been
  fired.

56
Documents

• CSIs collect any documents found at the scene
  such as diaries planners phone books or
  suicide notes
• Destroyed or burned documents can be
  reconstructed
• Handwriting analysis can be performed to link a
  crime scene and suspect

57
On the Stand

• CSIs must testify in court about the evidence
  collected
• CSI also testifies about the procedure and the
  people who came into contact with the evidence
• A defense attorneys job is to attack the
  evidence and have it thrown out of court
• Undisputable documentation of the crime scene are
  prime consideration