Detailed Notes on Crime Scene Investigation

Crime Scene Investigation Process

Introduction

Sergeant David Belden, a police officer with over 30 years of experience, including 25 years with the forensic response section. The forensic response section handles crime scene investigations for major crimes like homicides, attempted murders, and stranger rapes.

Crime Scene Investigation Process: Eight Steps

The crime scene investigation process consists of eight steps:

  1. Assessment
  2. Control
  3. Preservation
  4. Examination
  5. Interpretation
  6. Recording
  7. Collection
  8. Case Management

The amount of time spent on each step varies depending on the complexity of the crime.

1. Assessment

Assessment involves determining if a crime has taken place by ascertaining the when, where, and what of the event. This may be done by members of the public, fire officers, ambulance officers, or nurses. The goal is to identify potential crime scenes and evidence to protect and collect.

Example: Arson Investigation

An example involves a fatal fire initially believed to be accidental but was later investigated as homicide due to a missing louver from a rear window. Fingerprints on the window indicated a potential break-in. Removing debris from the house revealed the fire started in a bedroom wardrobe. The phone line had been cut, indicating sinister intentions. Fingerprint analysis identified a suspect who admitted to breaking in, cutting the phone line, and setting the house on fire to destroy evidence.

  • Tools used: Fingerprints
  • Investigating fires: Joint investigations with the South Australia Metro Fire Service.
2. Control

Control involves establishing and maintaining control of the crime scene, usually by the first officer on the scene. The priority is to prevent unauthorized access to avoid contamination or destruction of potential physical evidence.

Example: Shooting Homicide in Myers Centre

The entire Myers Centre was evacuated for a day to investigate a shooting homicide.

  • Tools used: Ballisticians for interpreting and reconstructing shooting events.
  • Ballisticians identify firearms, bullets, projectiles, and cartridges, and analyze range and trajectory.
3. Preservation

Preservation is paramount to ensuring that potential evidence is protected and in the best possible state for analysis and interpretation. This may involve using tarps to protect from weather or preventing evidence from being trampled.

Example: Burial Site in Adelaide Hills

Inflatable tents provided by the SES were used to protect a burial site from rain for four days.

4. Examination

Examination involves a detailed and systematic search of the crime scene to identify potential physical evidence. Experience and knowledge of the investigator are crucial in identifying potential evidence.

Fingerprints:

Various fingerprinting techniques include white powder, aluminum powder, black powder, magna powder, superleaf fuming, and ninhydrin. The fingerprint bureau conducts specialized fingerprinting searches and identifications maintained in the National Automated Fingerprint Identification System (NAFIS), which contains about 2,800,000 sets of prints.

Luminol:

Luminol is used to detect trace amounts of blood. For example, in a house where an assault was suspected but no visible evidence was found, luminal examination revealed blood, indicating something had happened. Another example involved a rug found in a washing machine, where luminal examination revealed blood stains.

Forensic Light Sources:

Forensic light sources, such as polylight, are used for locating biological fluids like semen. An example was provided in which multiple semen samples were found in different cubicles of a nightclub restroom after a reported rape.

Blood Pattern Analysis:

Blood pattern analysis is used to identify what has taken place by examining the location, size, shape, and distribution of bloodstains. For example, blood pattern analysis helped determine that an injured man's account of an assault was more consistent with the evidence than the account provided by his girlfriend and her new boyfriend.

Post Blast Analysis:

Post blast analysis determines the type of explosive involved, the detonation chain, how the device was delivered, and how it was activated. For instance, fragments from a post pack bombing were analyzed to determine the type of explosive used.

Physical Comparative Analysis:

Physical comparative analysis includes pattern transfer (tool marks, shoe marks), pattern fits (fracture matches), video/image analysis (clothing, firearms), and continuity (patterns on broken objects). Metal fragments from a bombing were matched to the wheel of an electric can opener through tool mark comparisons.

5. Interpretation

Interpretation of evidence to get a series of events, and blood pattern etc.

6. Recording

Recording involves documenting the crime scene using notes, photographs (now digital), 3D scanning, plans, and exhibit logs. 3D crime scene recording, using the Pharoscan, captures the crime scene in three dimensions, creating a point cloud model for producing plans, 3D models, and taking measurements. This can be done in complete darkness and is particularly useful for major crimes and commissioner inquiries.

7. Collection

Collection involves gathering evidence using various methods designed to maximize potential evidence and avoid degradation, including packaging, labeling, and maintaining continuity (chain of evidence). Various techniques such as adhesive lifting, absorption mediums, hand-picking, inking, Microsil (silicon casting), Trackstone (dental stone), scraping, swabbing, sweepings, and vacuuming are employed.

8. Case Management

Case management is the follow-up to the crime scene investigation, including preparing reports, liaising with investigators, scientists, and prosecutors, and determining which exhibits need to be analyzed. This involves determining what evidence either proves or disproves the offense, discussing testing sequences with forensic scientists, and considering potential destruction of exhibits, starting with the least destructive techniques. The process culminates in preparing a report for the court and giving evidence in the supreme court.

Conclusion

The crime scene investigation process involves assessment, control, preservation, examination, interpretation, recording, collection, and case management. Each step is crucial in ensuring that potential evidence is identified, protected, and accurately analyzed to bring offenders to justice.

Tools Mentioned

  • Fingerprints
  • MFS Equipment
  • Professor Bayard
  • Pathology at the Forensic Science Centre SA
  • Ballisticians
  • SES
  • Luminol
  • Forensic Light Sources (Polylight)
  • 3D Crime Scene Recording (Pharoscan)
  • Amido Black
  • Leuko Crystal Violet