Crime Scene Investigation: Evidence, Team Roles, and Procedures

What is the primary goal of crime scene investigation?

To recognize, document, and collect evidence at the scene of a crime.

What does Locard's Principle of Exchange state?

Whenever two objects come into contact, there is an exchange of materials between them.

What factors determine the extent of material transfer according to Locard's Principle?

The intensity, duration, and nature of the materials in contact.

What is a known standard in evidence analysis?

A sample with a known identity or concentration used for comparison with an unknown piece of evidence.

What is direct evidence?

First-hand observations such as eyewitness accounts, videos, or confessions.

What is circumstantial evidence?

Indirect evidence used to imply a fact but does not directly prove it.

Give an example of circumstantial evidence.

Finding a suspect's gun at a crime scene.

What are the types of circumstantial evidence?

Physical evidence, biological evidence, and trace evidence.

What constitutes physical evidence?

Fingerprints, imprints, tool marks, glass, soil, fibers, bullets, shell casings, drugs, etc.

What is biological evidence?

Body parts, body fluids, plant parts, natural fibers, feathers, wood, etc.

What is trace evidence?

Small but measurable amounts of physical or biological material found at a crime scene.

Why is circumstantial evidence important?

The more circumstantial evidence there is, the greater weight it carries in establishing probability.

What is class evidence?

Evidence that narrows down to a group of persons or things, such as blood type.

What is individual evidence?

Evidence that narrows down to a single person or thing, such as fingerprints or DNA.

How can class evidence become more individualized?

By narrowing it down through characteristics like brand, material, size, and color.

What is an example of class evidence?

Blood type, which can be A, B, AB, or O.

What is an example of individual evidence?

Fingerprints, handwriting, or DNA.

What role does probability and statistics play in circumstantial evidence?

They help determine the weight of circumstantial evidence in relation to the case.

What types of evidence might be considered trace evidence?

Strands of hair, fingerprints, DNA, drops of blood, pollen, etc.

What is the significance of analyzing evidence?

To identify physical or chemical properties and provide comparisons between unknown specimens and known standards.

What are the three types of evidence mentioned in the notes?

1. Evidence that proves a crime has been committed and sets the scene (e.g., gasoline at a fire scene). 2. Evidence that backs up or disproves witness testimony. 3. Evidence that links a suspect to a victim or crime scene.

What is the importance of evidence in a crime scene investigation?

Evidence can prove a crime has been committed, back up or disprove witness testimony, link suspects to victims or crime scenes, determine identities of individuals involved, and allow reconstruction of the crime.

Who are the first responders at a crime scene?

Police Officers.

What is the primary responsibility of police officers at a crime scene?

To secure the scene and direct activities.

What role do district attorneys play in crime scene investigations?

They may determine whether a search warrant is necessary for Crime Scene Investigators.

What tasks do Crime Scene Investigators perform?

They develop a detailed, technical written record based on observations, sketch the scene, take photos, and document the examination of the crime scene.

What is the role of medical examiners in crime scene investigations?

To determine the manner of death (natural, accidental, homicide, suicide, or undetermined).

What is the purpose of detectives in crime scene investigations?

To interview witnesses, Crime Scene Investigators, and specialists to gather evidence for reconstructing the crime.

What types of specialists may be involved in a crime scene investigation?

Forensic scientists, forensic anthropologists, botanists, entomologists, and forensic pathologists.

What is the first step in the Seven S's of Crime Scene Investigation?

Secure the scene.

What must be done to secure a crime scene?

Ensure safety of individuals, preserve evidence, isolate the area, exclude unauthorized personnel, and keep a security log.

Why is it important to separate witnesses at a crime scene?

To prevent collusion and ensure that their accounts can be compared independently.

What questions should be asked when questioning witnesses?

When did the crime occur? Who notified law enforcement? Who is the victim? Can the perpetrator be identified? What did you see happen? Where were you when you observed the crime?

What is the purpose of scanning the scene in crime scene investigation?

To assess the scene for evidence and determine the next steps in the investigation.

What does the 'search for evidence' step entail?

Thoroughly examining the crime scene to locate and collect evidence.

What protective measures must all team members take at a crime scene?

Wear protective gear to prevent contamination of the crime scene.

What is the significance of blood splatter analysis in crime scene investigations?

It can show the relationship between the suspect and victim and indicate the sequence of events.

How does evidence contribute to reconstructing a crime?

It allows investigators to piece together the sequence of events and understand how the crime was committed.

What does the term 'collusion' refer to in the context of witness separation?

Witnesses working together to create a false narrative or story.

What is the role of forensic anthropologists in crime scene investigations?

To analyze human skeletal remains to determine identity and cause of death.

What is the role of forensic pathologists in crime scene investigations?

To examine bodies to determine the cause and manner of death.

What is the purpose of documenting the crime scene?

To create a detailed record of the scene for legal and investigative purposes.

What was the goal of the Innocence Project, created in 1992?

To reexamine post-conviction cases.

What is the single greatest cause of wrongful convictions nationwide?

Eyewitness misidentification, playing a role in nearly 75% of convictions overturned through DNA testing.

How does social science research view eyewitness identification?

It has proven that eyewitness identification is often unreliable.

What analogy is used to describe human memory in relation to eyewitness testimony?

Witness memory is like evidence at a crime scene; it must be preserved and retrieved methodically to avoid contamination.

What is the primary crime scene?

The location where the crime actually occurred.

What is a secondary crime scene?

A location related to the crime but not where the actual crime took place.

What documentation methods are used by crime scene investigators?

Photographs and audio recordings of the scene.

What should be included in the rough sketch of a crime scene?

A title block with case information, a scale of proportions, and measurements of important objects from two immovable landmarks.

What is the purpose of sketching the crime scene?

To create an accurate representation of the scene for later presentation in court.

What factors influence the search pattern for evidence at a crime scene?

Size and type of location, whether it is indoor or outdoor, number of personnel, and available equipment.

What must investigators ensure during the evidence search?

No area is left unsearched.

What tools may be used to help find trace evidence during a search?

A flashlight or black light.

What should be done with evidence found at a crime scene?

It should be marked, photographed, and sketched.

What is the importance of eyewitness testimony in legal proceedings?

It can be persuasive evidence before a judge or jury.

What must investigators discriminate between when evaluating eyewitness testimony?

Fact and opinion.

What example illustrates the potential for misinterpretation in eyewitness testimony?

An innocent bystander running from a crime scene may be mistaken for the shooter.

What is the significance of the rough sketch in crime scene investigation?

It serves as a preliminary representation that will be refined into a final sketch for court.

What should be documented in photographs taken at a crime scene?

Overall area and close-up photos with and without a measuring ruler.

What is the role of forensic crime scene investigators?

To scan the scene, determine photo locations, and identify primary and secondary crime scenes.

What is the purpose of a title block in a crime scene sketch?

To provide information about the case, including date, time, location, case number, and names.

What is the first step in the crime scene investigation process?

Scanning the scene.

How does the type of crime affect the evidence collection process?

It impacts the type of evidence to be collected and the search strategy employed.

What must be done to all evidence during collection?

All evidence must be properly packaged, sealed, and labeled using specific procedures and techniques.

What type of containers are preferred for storing hairs, glass, and fibers?

Plastic pill bottles with lids are preferred containers for these types of trace evidence.

How should bloodstained materials be packaged?

Bloodstained materials must be packaged in wrapping paper, manila envelopes, or paper bags to prevent mold growth.

Why is airflow important when packaging biological evidence?

Air must be able to flow around the evidence to prevent moisture buildup, which can lead to mold contamination.

What type of container is used for charred debris from a fire?

Charred debris must be sealed in an airtight container, such as new metal paint cans.

What is a paper bindle and how is it made?

A paper bindle is made by creasing a sheet of clean paper into 9 grids, placing evidence in the middle, folding the sides in, and sealing it with tape.

What must be included in an evidence log?

The evidence log must include case number, item inventory number, description of evidence, names of suspect and victim, date and time of recovery, and signatures of the person recovering evidence and any witnesses.

What is the chain of custody?

The chain of custody is the documented and unbroken transfer of evidence, listing all persons who came into possession of the evidence.

What are control samples and why are they important?

Control samples are taken from the victim and others at the scene for exclusion purposes; they are crucial for comparison with crime-scene evidence.

What types of samples should be obtained when there is bloodstained evidence?

A whole blood sample or a buccal (cheek) swab must be obtained from crime scene participants.

What is the role of a forensic lab in evidence processing?

A forensic lab processes all the evidence collected by the CSI team, with technicians specializing in specific types of evidence.

What is the purpose of crime scene reconstruction?

Crime scene reconstruction allows detectives to hypothesize the sequence of events surrounding the crime.

What are some common types of staged crimes?

Common staged crimes include arson, murder staged as a suicide, and burglary.

What should be initially considered in all death investigations?

All death investigations should initially be treated as homicides.

What factors should be evaluated to determine if a crime scene is staged?

Factors include matching wounds to the weapon, establishing victim profiles, evaluating behaviors of the victim and suspects, and corroborating statements with evidence.

What is the significance of direct evidence compared to circumstantial evidence?

Direct evidence is generally more convincing than circumstantial evidence.

What happens to laboratory results after evidence processing?

Laboratory results are sent to the lead detective for interpretation and investigation.

Why is it important for crime scene investigators to include standard/reference samples?

Including standard/reference samples is crucial as evidence may be meaningless without them.

What is the procedure for sealing a paper bindle?

The top flap of the bindle is inserted into the bottom flap, taped closed, and placed inside a plastic or paper evidence bag with a seal over the folded edge.

What is the purpose of the evidence log?

The evidence log serves to document the details of the evidence collection process and maintain a record of the evidence's chain of custody.

What must be done with evidence to ensure it is admissible in court?

Proper procedures and protocols must be followed in handling evidence from the crime scene to the courtroom.

How can investigators support their hypotheses about a crime?

Investigators use scientific laws and theories to help form and support their hypotheses about what may have occurred.