Week 7 - Crime Scene Investigation Flashcards
Why is it crucial to recognize and collect physical evidence correctly?
If evidence is missed, mishandled, or contaminated, the case can be compromised and lost.
What are identification officers, and who typically fills this role?
Identification officers, or Ident officers/technicians, are usually sworn police officers with 3+ years of general duty experience. Some scientists have now joined these roles as civilians.
What are the key steps in becoming a crime scene identification officer?
three week assessment
written exam
basic ident course
understudy
six hour 90% exam
mock trial
continual training
What ongoing training must a crime scene identification officer complete?
Officers must maintain their certification through continual training and engage with organizations like the Canadian Identification Society and the International Association for Identification.
What is the typical sequence of events at a crime scene?
A crime is reported or discovered.
First responders arrive to determine if a crime has occurred.
A police officer takes control of the scene.
Priorities: Police safety, victim safety, public protection, and evidence preservation.
First responders notify support sections, such as ident officers, serious crime teams, and the coroner.
What are the responsibilities of first responders at a crime scene?
must ensure police and victim safety, protect the public, and preserve the crime scene and evidence.
What is the role of the forensic identification section at a crime scene?
identifying and collecting evidence, such as pattern evidence like prints and blood, and then taking it to the lab.
What does the serious crime section do?
handle the investigation, analyze reports from specialists (e.g., toxicologists, entomologists), and work with police and detectives
What is the role of the coroner’s service at a crime scene?
may attend the scene but will always call forensic pathologists to perform autopsies. They also coordinate with body removal services.
What should be done if the victim is still alive at the crime scene?
priority is to save the victim, even though this may destroy evidence. The victim is also a key witness
What should be done if the victim is dead at the crime scene?
victim’s body should not be disturbed. Emergency personnel determine the victim is dead, and then back off, leaving all equipment behind until the ident specialists arrive
What are the duties of first responders at a crime scene?
safety of police, the public, and the scene
protect and secure the area by posting guards and setting up barricades
must not interfere with evidence unless it is perishable, in which case they can cover it.
How are rural crime scenes handled differently from urban ones?
In rural areas, first responders typically block trails but try to avoid cutting off too large an area from access.
What are the legal and scientific responsibilities of an ident specialist at a crime scene?
Identify each piece of evidence.
Describe exactly where each piece of evidence was found.
Prove continuity by stating where the evidence has been at all times.
Describe any changes in the evidence (e.g., melted ice cream).
How does an ident specialist ensure the continuity of evidence?
tracking and documenting the evidence from the moment it’s collected, including any changes to its condition and where it has been at all times
What does an ident specialist do before entering the crime scene?
gather more information by talking to first responders about:
Obvious evidence that had to be moved.
What the scene contains.
What has been disturbed.
What witnesses have said.
Any other valuable information.
What is Locard’s Exchange Principle and how does it apply to crime scenes?
that in every contact, there’s an exchange of evidence:
The killer leaves evidence behind and takes evidence with them.
Even a police officer can unintentionally do the same.
How do officers protect the crime scene from contamination and protect themselves?
wear protection suits (bunny suits) to cover their entire body, preventing contamination of the scene and protecting themselves from biohazards.
What are the key features of an officer protection suit?
Thin, paper-like material.
A hood to prevent hair from shedding.
Two pairs of gloves for ease of removal.
A face mask to prevent saliva and DNA transfer.
Suits and gloves are changed regularly, especially during breaks.
Why are elimination samples important at a crime scene?
exclude DNA, boot prints, and fingerprints from first responders or emergency personnel who were not wearing protection suits
What can happen if officers are not properly attired at a crime scene?
risk contaminating the scene or being accused of contamination, which can compromise the investigation.
How did contamination affect the O.J. Simpson case?
In the O.J. Simpson case, police walked through bloody footprints without proper protection, raising concerns about evidence contamination.
How is a crime scene examination typically conducted?
slow, laborious, and precise. Every detail is documented, and it can take days to complete.
pickton - 18 months
How do investigators choose a path to enter a crime scene?
use the least likely route to avoid disturbing evidence.
Indoors: Enter through the back door or edges of rooms.
Outdoors: Go through underbrush rather than the obvious trail.
Why do investigators use the least obvious route when entering a crime scene?
Because the killer likely used the most obvious routes, and investigators want to protect that evidence.
What is a safe zone or zone of contamination in crime scene processing?
a designated area that is searched and used as the access point for personnel to prevent contamination of the main crime scene.
What are the key responsibilities of an ident specialist at a crime scene?
Preserving and protecting evidence.
Taking photographs (still and video).
Writing detailed notes.
Searching the scene.
Sketching, measuring, and drawing objects.
Collecting and recording evidence.
What is the importance of note-taking at a crime scene?
copious and the most detailed possible. They serve as crucial evidence in court
secure several notebooks per case, and also use tape recordings and sketches
What steps are taken when searching a crime scene?
Potential evidence is sketched, noted, measured, and photographed before it is seized.
What are the three types of photos taken at a crime scene?
Overview – A wide shot capturing the whole scene.
Intermediate – Closer to the evidence but still shows its relation to the entire scene.
Close-up – A detailed shot of the evidence.
Why are close-up photos alone not enough?
don’t provide context; they need to be part of a series that includes overview and intermediate shots to tell the complete story
Why is a scale used when photographing evidence?
measure the size of evidence and are essential for accuracy in tight areas, ensuring the photo is properly aligned and not distorted by the camera angle.
What is an ABFO scale and how is it used?
right-angled tool with circles and lines to determine if a photo was taken at an angle. It’s used to ensure accurate measurements
What are some common methods used to search a crime scene?
grid, line, zone, spiral, wheel, and quadrant/zone
What is the preferred search method for a crime scene and how is it done?
grid search is preferred. The scene is divided into small grids (30–100 cm squares), and each grid is assigned XY coordinates based on a permanent structure like a road or building.
When is a line or strip search used, and why?
outside areas and is especially useful when dealing with scattered remains or when the crime scene covers a long area.
What is a zone search, and when is it used?
A zone search is similar to a grid search but involves much larger areas.
Indoors: Each room is treated as a zone.
Outdoors: Used for large areas.
How is a spiral search conducted?
starts at the outside of the scene, and a single person walks in a spiral pattern toward the center of the crime scene.
difficult to make a perfect spiral, so there’s a risk of missing evidence.
How is a wheel or ray search carried out?
Multiple people move from the boundary to the center of the scene in straight lines, like spokes on a wheel.
Evidence between the spokes may be missed
Drawing and Measuring the Scene
Evidence is recorded using XY coordinates, with reference to fixed points
precise measurements of evidence in relation to other pieces
compass heading helps determine the direction and orientation of evidence
What is a total station, and how is it used in crime scene investigations?
surveying tool, often used in vehicular accident reconstructions, that uses a theodolite to measure distances, angles, and slopes.
What key information must be included when seizing evidence?
flow chart should document:
What the evidence is
Where it was collected
Who collected it
Time of collection
Exhibit number
Other relevant data
How is wet evidence like blood or semen collected?
Wet evidence is collected using paper to allow it to dry and prevent mold or contamination.
Paint evidence is folded into paper
How is dry evidence like dust or fibers collected?
typically collected in plastic containers.
Give an example of how bloodstain patterns led to identifying a suspect.
blood stains were all over an apartment, but one stain had a different pattern. Years later, it was found to belong to the boyfriend
What is the chain of custody, and why is it important?
process of recording and documenting where evidence is at all times to prevent contamination and maintain its integrity
What happens if continuity of evidence is not maintained?
accusations of contamination, and the evidence may be discredited.
How is a decomposed body handled differently from a fresh body?
decomposed body may require more scene examination before being moved, while a fresh body is taken directly to the morgue.
What is done to the body at the scene before it’s moved?
Check for ID (e.g., wallet)
Insects/plants are collected
Hands, feet, and head are bagged with paper to prevent loss of evidence or mold growth.
How is body continuity maintained after death?
coroner calls a body removal service (BRS), and the body is placed in two body bags
police officer escorts the body, places it in a secure crypt, and keeps the only key until the autopsy
Who attends the autopsy, and why?
ident officer attends the autopsy to collect additional evidence, such as clothing, visual examination, and internal evidence like bullets.
How can evidence be cross-contaminated from another crime scene?
investigators move between scenes without proper precautions, transferring blood or DNA from one scene to another.
What is a case history example involving multiple crime scenes?
Scene 1: Apartment – dead woman.
Scene 2: Nearby house – dead parents.
Scene 3: Man drove to the police and gave himself up.
Victim 1’s blood was found on a knife in the sink of Victims 2 and 3.
Blood of all three victims was found in the car.
three separate ident teams ensured that evidence, like blood, could not be argued as moved between scenes
Who was Lukis Anderson, and why was he accused of murder?
DNA was found on the victim.
Anderson was unconscious and drunk in the hospital at the time of the murder
Paramedics who had handled Anderson earlier transferred his DNA to Kumra
What is hold-back information, and why is it important?
key fact about the crime that is kept secret from everyone, including other police, media, and family.
only the eyewitness, investigator, or killer knows the specific detail
Why are families not allowed into the crime scene?
unknowingly transfer DNA or evidence, which could contaminate the scene. Additionally, family members are sometimes suspects.
How do large U.S. cities handle crime scene investigations?
many specialists who handle specific tasks like photography and fingerprinting, with many investigators involved in different scenes
higher the risk of contamination
What is the issue with fingerprint analysis being police-driven?
lacks the scientific rigor seen in other fields
population studies or error rate analysis.
based on experience, and claims of zero error rates are not scientifically plausible.
What is the ACE-V method, and what did NAS find about it?
NAS reviewed this method and found no scientific evidence supporting its validity, noting it does not prevent bias
What factors lead to variability in fingerprint impressions?
Pressure, angle, surface contact, and the medium used all contribute to variability in the impressions left by the same finger
How does cognitive bias manifest in fingerprint analysis?
incorrect match was declared due to overconfidence and the urgency of the investigation
What did the bias experiment reveal about fingerprint examiners?
50% of the examiners were given contextual information like a confession or alibi. About 25% of them changed their original identifications based on this manipulation
What new research does the PCAST report call for in fingerprint analysis?
Measure reliability
Understand the factors that impact decision-making
Make the process less subjective
ACE-V method is problematic because it is not blind, which leads to confirmation bias.
false positives are much higher than the public believes.
