Two General Types

• Testimonial Evidence: a statement made under oath; also known as direct evidence or Prima Facie evidence

• Physical Evidence: any relevant object or material in a crime; also known as indirect evidence. Examples are hair, fiber, fingerprints, documents, blood, soil, drugs, tool marks, impressions, glass.

Reliability of Eyewitness

• Factors that must be considered:

  • Mature of the offense and the situation in which the crime is observed

  • Characteristic of the witness

  • The manner in which the information is retrieved

• Additional Factors:

  • Witness’s prior relationship with the accused or victim

  • Length of time between the offense and the identification

  • Any prior identification of a person other than the defendant by the eyewitness 

Eyewitness

• A police composite may be developed from the witness testimony by a computer program or a forensic artist

• “Perception is reality to an eyewitness”

• Because of the influences in eyewitness memory, physical evidence becomes critical.

  • Physical evidence has to corroborate with what the witness says

Eyewitness Identification 

• Ronald Cotton Case

  • A woman was raped and there was a sketch. Then they brought in a bunch of men and chose who it was and he was arrested

  • As time went on she was concerned that it wasn’t the person

  • Several years later there was a man who was arrested and the man who was arrested was not the criminal

Hearsay Rule

• Testimonial evidence or documentation that quotes a person/s NOT in court is NOT admissible.

• “Drew’s Law”:

  • The media coined it because of a landmark case against Drew Peterson.

  • The State of Illinois passed a law (2008) that would allow hearsay evidence if the prosecutors believe that a victim was killed to prevent his/her testimony (CNN, Jan 2010).

Physical Evidence: any and all objects that can establish that a crime has been committed or can provide a link between a crime and its victim or a crime and its perpetrator.

Value of Physical Evidence:

• Generally more reliable than a testimonial if it is clear and useful

• Can prove that a crime has been committed

• Can corroborate or refute testimony

• Can link a suspect with a victim or with a crime scene

• Can establish the identity of persons associated with a crime

• Can allow the reconstruction of events of a crime. 

Reconstruction of the Crime

• Physical Evidence is used to answer questions about:

  • What took place

  • How the victim was killed

  • Number of people involved

  • Sequence of events

• ****A forensic scientists will compare the Questioned or unknown crime scene sample of evidence with a sample of Known origin (which is the control).

Types of Physical Evidence

• ***Evidence can be in more than one type

1. Transfer Evidence: produced by contact between person(s) or object(s), or between person(s)

   1. Ex: blook swipe

2. Associative Evidence: items that may associate a victim or suspect with a scene or each other

   1. Ex: personal belongings

3. Transient Evidence: temporary; easily changed or lost; usually observed by the first officer at the scene.

   1. Ex: Odor - putrefaction (smell of decomposition), perfume, gasoline, urine, burning, explosives, cigarette or cigar smoke

   2. Temperature - surroundings, car hood, coffee, water in a bathtub, cadaver

   3. Imprints and Indentations - footprints, teeth marks in perishable foods, tire marks on certain surfaces, markings in dust or mud

4. Pattern Evidence: produced by direct contact between a person and an object or between two objects where a pattern is produced that can be interpreted by a professional

   1. Most types are in the form of imprints, indentations, striations, markings, fractures, or deposits

   2. Ex: blood spatter, glass fracture, fire burn pattern, projectile trajectory, ture marks, clothing or article distribution, gun powder residue, tool marks, modus operandi (method or pattern of how a killer does his ‘job’)

5. Conditional Evidence: produced by a specific event of action; important in crime scene reconstruction and in determining the set of circumstances or sequence within a particular event

   1. Ex: lights - headlight, lighting conditions

   2. Fire - color and direction of the flames, speed of spread

   3. Location - of injuries, of bloodstains, of the victim's vehicle, of weapons of cartridge cases, of broken glass

   4. Vehicles - doors/windows locked or unlocked/open or closed, radio off or on, odometer mileage

   5. Body - position, types of wounds; state of mortise

   6. Scene - condition of furniture, doors, and windows, and disturbance or signs of struggle

Another way to Classify Evidence is by Nature:

• Biological: blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacterial, fungal, botanical

• Chemical: soil, gunpowder, metal, mineral, narcotics, drugs, ink, cosmetics, paint, lubricants, fertilizer

Evidence Characteristics:

• Class: common to a group of objects or persons

  • Circumstantial Evidence: many pieces can increase the probative value of the case (not as strong as individual)

    • Ex: hair + soil type + fiber type

• Individual: can be identified with a particular person or a single source

  • Ex: fingerprints, DNA typing

  • If pieces can be fit together like a jigsaw

Forensic Investigations:

• Include some or all of these seven major activities

1. Recognition: the ability to distinguish important evidence from unrelated material

   1. Pattern recognition

   2. Physical property observation

2. Preservation: proper collection and preservation of evidence

3. Identification: use of scientific testing

   1. Ex: physical, chemical, or biological properties

4. Comparison: class characteristics are measured against those of known standards if all measurements are equal, then the two samples may be considered to have come from the same source or origin.

5. Individualization: demonstrating that the sample is unique, even among members of the same class

6. Interpretation: gives meaning to all the information

7. Crime Reconstruction: reconstructs the events of the case using:

   1. Inductive and deductive logic

   2. Statistical data

   3. Pattern analysis

   4. Results of laboratory analysis

The Body of a Crime:

• Top reasons for committing a crime:

  • Money

  • Revenge

  • Emotion - love, hate, anger, fear

• You must prove:

  • That a crime occurred

  • That a person charged with the crime was responsible for the crime

• Source of evidence:

  • Body

  • Primary and/or secondary crime scene

    • If a murderer kills someone and then moves the body, where they were killed is primary and where they were moved is secondary

  • Suspect(s)

Crime Scene Team

• A group of professional investigators, each trained in a variety of special disciplines.

  • Team Members:

    • First police officer on the scene

    • Medics (if necessary)

    • Investigator(s)

    • Medical Examiner - pathologist (if necessary)

    • Photographer and/or Field Evidence Technicians

    • Lab experts - forensics scientists

Processing a Crime Scene

1. Isolate and secure the scene

   1. So no one can contaminate the crime scene

2. Document the scene 

   1. Documenting and photographing the evidence and what the scene looks like

   2. Set the scene to set it up later on

3. Search for evidence

   1. What is evidence and worth the time and money

4. Collect and package evidence, maintaining the chain of custody

   1. Keep track of everyone who has been in custody of that evidence

5. Submit evidence to the crime scene

First Officer on the Scene (step 1)

• A - assess the crime scene and assist those hurt

• D - detain the witness

• A - arrest the perpetrator

• P - protect the crime scene

• T - take notes

Crime Scene Survey (step 1 and 2)

• Walk-through: performed by the crime scene investigator, the first officer, and sometimes the lead detective

  • Purpose:

    • Mentally prepare a reconstruction theory

    • Note any transient of conditional evidence that could change over time

    • Note weather conditions 

    • Note points of entry or exit, as well as paths of travel within the crime scene

    • Record initial observations of who, what, where, when, and how

    • Identify special needs within the crime scene for personnel, precautions, or equipment and notify superior officers or other agencies. 

Documentation (step 2)

• Notes: besides what was collected at the walk-through

  • Description of crime, location of the evidence, the names of all people involved

• Photography: photos of the scene and surroundings, close-up photos with various angles of each piece of evidence, and photos as viewed by any witnesses.

• Sketches: inclusion of date, time, scale, reference points, distance measurements, names of investigators, victims, suspects, and a legend (key)

• Videography: allows narration (non-subjective) to be included

Crime Scene Sketch (step 2)

• Triangulation: all evidence must be measured using 2 fixed points

• All sketches must include:

  • Name of investigator

  • Address of crime

  • Type of crime

  • Date

  • Legend/Key

  • Scale used 1/4in = 1 ft

  • Compass points

Search Methods

1. Line or strip method: best in large, outdoor scenes

2. Grid method: basically a double-line search; effective, but time-consuming

3. Zone methods: most effective in houses or buildings; teams are assigned small zones for searching

4. Wheel or ray method: best on the small, circular crime scene

5. Spiral method: may move inward or outward; best used where there are no physical barriers

Collecting and Packaging Evidence

• The Evidence Collection Unit’s responsibility:

  • To ensure that the evidence is collected, packaged, marked, sealed, and preserved in a consistent manner that prevents any change between the crime scene and the lab. 

  • Most fragile is collected and packaged first

  • Hairs, blood, and fibers should not be removed at the scene. The article it is on should be sent to the lab intact and the evidence removed there. 

    • If blood was on a couch, they would cut or take the whole cushion back to the lab and then collect the evidence. 

    • Some areas of the crime scene may be vacuumed and the sweeping submitted to the lab for testing.

• The body is the property of the medical examiner

• The following items obtained from the body are sent to the forensic lab for testing:

  • Victim’s clothing

  • Fingernail scrapings

  • Head and pubic hairs

  • Blood 

  • Vaginal, anal, oral swabs (in sex-related crimes)

  • Bullets recovered from the body

  • Hand swabs from suicide victims looking for gunshot residue

Packaging

• Each item must be placed in a separate container, sealed, and labeled

• Most items should be packaged in a primary container and then placed in a secondary container

  • So that it doesn’t get tossed around

• Different types of evidence require specific or special collection and packaging techniques such as paper bags, plastic bags, canisters, packets, and envelopes

  • Blood and other bodily fluids (and all clothing) should NOT be packaged in an airtight plastic container for longer than two days. Condensation will cause mold/bacterial growth which could ruin the evidence. 

  • Any charred debris MUST be packaged in an air-tight container so the petroleum residues do not evaporate (paint can and glass jars are often used. 

Obtaining Controls

• Any collected evidence (hair, fibers, soil, etc.) should be compared with a control (known sample) from the actual crime scene

• Bloodstain evidence must be accompanied by whole blood or buccal swab controls (inner portion of cheek) obtained from all relevant crime scene participants. 

Chain of Custody

• There must be a written record of ALL people who have had possession of an item of evidence

  • The evidence container must be marked for identification

  • The collector’s initials should be placed on the seal, state of collection, and the location of evidence

  • If evidence is turned over to another person, the transfer must be recorded

  • Chain of custody should be kept to a minimum

Submitting Evidence

• Submitting evidence to the lab

  • Evidence submission forms are required for all articles to be tested

  • Case history should accompany the evidence submission form so the analyst can examine the evidence in a logical sequence

  • The particular type of test should be noted, but the analyst is not bound to only that test, they can do additional tests they might think are helpful

Legal Considerations at the Crime Scene

• Any evidence at the scene must be removed in compliance with 4th amendment privileges

• Allowances for warrantless search:

  • The existence of emergency circumstances

    • There is a fire and they need to get certain things or they will be destroyed

  • The need to prevent the immediate loss or destruction of evidence

  • A search of a person or property within the immediate control of the person provided it is made incident to a lawful arrest

    • Has to be within sight

    • Can take your phone but can’t search for it without an arrest

    • If they arrest someone and they see marijuana, they can take it without a warrant

  • A search made by consent of the parties involved

• “Fruit from the poisonous tree”

Court Case Examples

• Mincey vs. Arizona - Drug Investigation 

• Michigan vs. Tyler - Arson Investigation