Forensics Unit 2: Crime Scene Investigation

Types of Evidence

Testimonial, Physical, Trace

What is testimonial evidence?

A statement made under oath by a competent witness.

What is hearsay?

A statement, other than one made while testifying, offered in evidence to prove the truth of the matter.

What kind of evidence can testimonial evidence be?

Direct or Circumstantial Evidence

What are characteristics that are most accurate from witnesses? Which are the least accurate?

Gender, hair color; age, height, race

What kind of witness is more accurate?

• A witness that is physically similar to the offender.

• A serious crime is committed.

Why don't children remember situations as well?

The testimony of children is more easily affected by interviewing techniques.

What affects memory and recall?

Learning disabilities, head injury, drugs/alcohol

What kind of questions should you ask?

Open ended

False accusations are caused by?

Mistaken eyewitness identification.

What is physical evidence?

Any object that can establish that a crime has been committed or can link a crime and its victim or its perpetrator.

How is physical evidence processed?

Comparing a questioned/unknown sample to a control/known sample.

Trace Evidence

Evidence that is small and often hard to find; comes from contact of objects.

Individual Evidence

A kind of evidence that identifies a particular person or thing.

Class Evidence

Common to a group of objects or persons.

Why is physical evidence valuable?

• Proves a crime has been committed and sets the scene for the investigation.

• Support of refuting witness testimony.

• Link a suspect with a victim or with a crime scene.

• Determine the identity of people associated with a crime.

• Allow investigators to reconstruct a crime.

What do crime scene investigators do?

They can develop links among the evidence, victim, crime scene, and perpetrator.

How can the links from the CSI help in a crime scene?

Can reconstruct the sequence of events, the modus operandi, and motive

What is the role of a first responder?

• Determines the nature of the crime.

• Gets assistance for the injured.

• Detains or arrests suspects.

• Isolates witnesses.

• Secures the crime scene, ensured that all evidence is contained within the closure.

• Records all activity.

• Remain on site until further staff arrives.

What is the role of a medical examiner?

• Note the body's condition.

• Estimate time of death.

• Protects physical evidence from tampering and destruction.

What is the role of an investigator?

• Interviews with victims, witnesses, police on scene, specialists.

• Responsible for the management of information given to the press.

• Discuss the evidence with the prosecutors' office to determine the legal direction of the investigation.

What are the three primary methods of documenting a crime scene?

Photography, Sketching, Notes

What do photographs prove?

• Captures important details not immediately observable.

• Scene must be photographed before touching or moving any evidence.

• Should include close-ups of evidence, views through the eyes of the witness, and at various angles.

• Ruler should be used for scale.

• Video recordings should begin outdoors and move indoors.

What do sketches show?

• Give perspective to the photographs.

• Rough sketches are done in situ; finished sketches are completed using CAD technology.

• Include measurements, scale, relative placement of all important details in the crime scene.

• Should also include artist's name, date/time, reference points, and a legend.

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What do notes provide?

• One of the most important parts of processing the crime scene.

• Forces investigator to be more observant and enhances memory of details.

• Should include measurements, names/dates/times, locations, environmental conditions, description of crime.

• Audio recording can be helpful.

How do investigators search for evidence?

• The investigators are looking for anything that should not be there.

• Anything that might carry trace evidence should be collected.

• Special lighting may be used to spot invisible body fluids

• Large search areas may be searched with multiple investigators.

What are the types of search patterns?

Strip/line, grid, pie/wheel, spiral, zone/quadrant.

How to properly package evidence?

• Photograph the evidence.

• All evidence is collected and labeled individually.

• Reference samples should also be collected.

• Evidence should be sealed with tamper-proof tape.

• Label the package with identifying information.

• Sign/date/time of collector on package.

How do you package wet fluids?

• Collect with a sterile swab (if clothing, collect intact) and allow to air dry.

• Package in paper envelope/bag (blood refrig. or frozen w/in 48 h).

How do you package dry fluids?

• Collect/wrap items in the paper (leave blood intact!) and tape closed.

• Package in a paper bag or box.

How do you package hair/fibers/glass/paint?

• Collect with tweezers, place in paper bindle.

• Package bindle in envelope; large pieces of glass in box with cotton or tissue to prevent breakage.

How do you package firearms?

• Collect assembled with safety on and magazine/ammo removed.

• Package in heavy cardboard or wooden box.

How do you package tracks or toolmarks?

• Collect items in paper (leave mark intact!) and tape closed; if size is impractical, cast the mark.

• Collect items in paper (leave mark intact!) and tape closed; if size is impractical, cast the mark.

How do you package drugs?

• Collect in original containers, if possible, or separate paper/specialty containers.

• Package in box or larger envelope.

How do you package fingerprints?

• Collect items (leave prints intact!) or individual prints by lifting.

• Package in appropriately sized container allowing little to no movement within.

How do you package documents?

• Collect intact; charred documents with ash.

• Package cellophane or plastic envelope; charred placed on cotton in a box.

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How do you package bullets/cartridges?

• Collect with tools to avoid scratching

• Package in box or larger envelope

What is the Chain of Custody?

• "Paper trail" showing the seizure, custody, control, transfer, analysis, and disposition of evidence, physical or electronic.

What is the importance of the chain of custody?

Recording the chain of custody is to withstand legal challenges to the authenticity of the evidence.

Evidence

criminal evidence acquired through scientific methods, including ballistics, blood tests, and DNA tests to be used in court.

Class evidence

consists of substances such as blood and hair, which can be used to place an individual in a general class but cannot be used to identify an individual.

Individual evidence

anything that can be linked to a unique, single, specific source.

Physical evidence

any tangible object that can connect an offender to a crime scene

Direct evidence

evidence that, if believed, directly proves a fact.

Indirect evidence

(also called circumstantial evidence) is a fact or set of facts that, if true, allow jurors to infer the fact at issue

Spiral search

• the investigator(s) examining the area for evidence in an ever widening circle, from the position of the core crime scene or on the perimeter and then moves in an outward direction.

Parallel search

Crime scene investigators form a line and walk parallel to each other at the same speed from one end of the crime scene to the other

Grid search

Several searchers, or a line of them, move alongside each other from one end of the area to be searched to the other.

Zone search

breaks the crime scene area into squares.

Chain of custody

A process that tracks the movement of evidence through its collection, safeguarding, and analysis lifecycle by documenting each person who handled the evidence, the date/time it was collected or transferred, and the purpose for the transfer.

Standard reference sample

Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime scene evidence.

Fourth amendement

rule is that an investigator executing a search warrant is able to look in any place listed on the warrant where evidence might conceivably be concealed.

Responding officer

the officer who responds first to the scene

Crime scene investigator

person responsible for documenting the crime scene. They take photographs and physical measurements of the scene, identify and collect forensic evidence, and maintain the proper chain of custody of that evidence.

Crime scene report

Photography, video recording, sketches and notes

Crime (in terms of forensics)

provides the criminal justice system with evidence that could be used to convict a suspect even when an eyewitness is not present.

Felony

an offense, as murder or burglary, of graver character than those called misdemeanors, especially those commonly punished in the U.S. by imprisonment for more than a year.

Misdemeanor

any offense other than a felony or treason

Infraction/Violation

Violation of a rule or law that isn't punishable by prison; penalty is usually a fine.