SUPA Forensics Midterm

4th Amendment

• “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Process of Search and Seizure

• A judge must approve any search and seizure of items

• In order to get approval to search and seize items, an investigator must submit a search warrant to be read and signed by the judge

• Warrant is needed for biological samples → a discarded article is fair game, though

• The warrant must show probable cause: the current evidence and reasoning that demonstrates a likelihood that the item related to the incident will be in possession of the person

  • It must specify:

    • The item(s) sought

    • The location to be searched

    • The time the search will be executed

Exclusionary Rule

• Any evidence gathered without a warrant or a justified warrantless search reason is inadmissible

• Ex. The locked trunk of a vehicle is illegally searched and an unregistered firearm is found 

Fruit of the Poisonous Tree Doctrine

• Any evidence developed from illegally obtained evidence is inadmissible 

• Ex. An address book is found in an illegally opened trunk, which contains the address of someone who is suspected of trafficking weapons. Anything found at that address (even if there is a warrant) is inadmissible because no probable cause would’ve existed without the illegally found evidence

Private Security Guards Exception

• They are employed by a private entity, and a citizen has a choice to interact with that entity

• Private security guards are allowed to do a warrantless search and notify law enforcement of any findings (which is probable cause for law enforcement to get a warrant)

Warrantless Searches (Exceptions to the 4th Amendment)

• Consent

  • Must be given by a legal adult

  • The area has to be under their legitimate control

  • Always best to get consent in writing

  • Ex. College dorm suites, tenants in a rented residence (not landlord)

• Plain view

  • With anything easily visible by a passerby

  • There is no expectation of privacy

  • Item may be searched and seized without a warrant

  • Ex. Transparent bags, dashboard/seats of cars

• Legal Arrests

  • As a safety precaution

    • The suspect may be patted down and relieved of possessions that are illegal/pose a threat to an officer

  • This extends to the suspect’s “area of control”

• Emergency Circumstances - Mincey v. Arizona

  • Case: Evidence collected without a warrant in a raid where officers were shot

    • Those officers couldn’t investigate/search the house

  • Officers may enter a structure without a warrant if there is an objectively reasonable belief that danger is imminent and harm is about to occur

• Prevent Destruction of Evidence - Michigan v. Tyler

  • Case: Evidence was seized during a fire

    • Firefighters re-entered and collected more evidence

  • Officers may enter a structure without a warrant to prevent the destruction of evidence if evidence is about to be lose

    • Only for limited duration

    • Volatile liquids (Accelerate evaporation)

• “Stop and Frisk” - Terry v. Ohio

  • An officer may stop a suspect on the street and frisk them without probable cause to arrest, if the police officer has a reasonable/articulable suspicion that the person has committed, is committing, or is about to commit a crime and has a reasonable belief that the person “may be armed and presently dangerous"

First Responder

• The first law enforcement individual on the scene

The First Responder’s Responsibilities

• Sequence of decisions is driven by protecting people from bodily harm (safety first)

• 1. Call for backup

  • Keep team informed of any needs/changes on the scene

  • Ex. Getting an ambulance or other specialist (bomb, hostage)

• 2a. Aid injured victims until medical personnel arrive

• 2b. Apprehend a dangerous suspect

  • Someone who could cause more bodily injury if left unchecked

  • Use of force applies

• 3. Render the scene/location safe

  • In the case of a leak, spill, or fire

  • Move bystanders away to safety

  • Move items to contain a spill (Ex. move gas cans away from a path of fire)

• 4. Secure the scene

  • Physically define the boundaries by roping/marking it off with crime scene tape

  • Protect it from alteration

    • Position officers to protect the perimeter

    • Redirect any traffic (foot, vehicular) around the area

    • Restrict movement of anyone into/out of scene

• 5. Document the scene

  • Capture the original state of the scene in as much detail as possible

  • Notes, rough sketches, photos, contact info for potential witnesses

Use of Force

• Officers will only use force when it is objectively reasonable and necessary and officers are obligated with intervening with any officer that oversteps the boundary

• Always based on officer training and experience

• Levels of Escalation:

  • Constructive Authority - Officer uses verbal commands, gestures, warnings, and unholsters weapon

  • Physical Contact - To help officer accomplish a legal objective (guiding subject into police vehicle, handcuffing a subject)

  • Physical Force - When someone actively resists authority or harms a person/property (ex. wrestling subject to ground, using wrist locks)

  • Mechanical Force - Some device or substance, other than a firearm, to overcome subject resistance (ex. baton, canine, chemical sprays, taser)

  • Deadly Force - Purpose of causing death or serious bodily harm (ex. firearm)

When are police authorized to use force?

• To overcome resistance directed at the officer

• To protect the officer or a 3rd party from unlawful force

• To protect property

• To effect other lawful objectives, such as to make an arrest

When are police authorized to use Deadly Force?

• When the officer believes that such action is immediately necessary to protect the officer or another person from imminent danger of death

• To prevent the escape of a fleeing subject

  • Suspect must have just attempted to kill/did kill someone AND

  • Will pose a threat of death to someone if they escape AND

  • The use of deadly force poses no risk to innocent people

• The goal of using a firearm is to neutralize the threat, and the target is the torso

Imminent Danger

• If no action is taken, there will be a threat to someone’s life (does not have to be instantaneous)

Substantial Risk

• Exists when law enforcement disregards that innocent people might be harmed

• Ex. firing a weapon in a confined space

Steps of securing the scene

• Prevent unrelated bystanders from entering the scene

  • They could remove items from the scene, add items to the scene (which could mislead investigators into wasting resources pursuing the wrong path), and alter the arrangement of items at the scene (which misleads the reconstruction of events)

• Prevent related bystanders from entering the scene

  • They could remove items from the scene, add items to the scene (which could mislead investigators into wasting resources pursuing the wrong path), and alter the arrangement of items at the scene (which misleads the reconstruction of events)

  • They could have a motive to intentionally tamper with the scene

• Never allow a suspect back on the scene

  • They could remove items from the scene, add items to the scene (which could mislead investigators into wasting resources pursuing the wrong path), and alter the arrangement of items at the scene (which misleads the reconstruction of events)

  • They could have a motive to intentionally tamper with the scene

  • Creates a question of time (it becomes unclear when evidence linking the suspect to the scene was deposited)

• Prevent law enforcement without an assigned task from entering the scene

  • Anyone who works the scene must sign in/out

  • Must have their known samples collected and stored for comparison

• Communicate certain information to the media

  • Tell public about imminent threat 

  • Don’t share private information or allow the public to know too much

Crime Scene Coordinator

• The person overseeing the systematic processing of the scene and its evidence

How should a CSI team enter and exit a scene?

• Through 1 route

  • However the first responder entered the scene is how all CSI personnel enter and exit

  • Done so that the scene will be as undisturbed as possible

Sequence of Tasks of the CSI team

• Document the scene

  • In more detail than first responder

  • Notes, sketches, video, photo, audio

  • They can’t rush - they only get one chance to do it right

• Recognize evidence

  • Mark each item separately

  • Use sequential, numbered evidence markers

• Search the scene

  • Helps to hypothesize what might be found

  • Different search patterns based on scene

• Collect, package, and label evidence

  • Every item gets its own container

• Transport to Evidence Storage/Lab

Importance of documenting the scene completely

• For memory

  • People don’t always recall details

  • People may not have been at the scene

  • Cases can take a long time to solve

• Legal purposes

  • Can back up/prove claims in court

• Scientific purposes

  • Unexpected test results can be explained

What should be included in notes of a scene?

• Smells/odors

• Lights (on/off)

• Doors (open/shut)

• Date/time

• Location (where)

• Items

• Position (how it’s oriented)

• Address

• Investigators present

• Measurements 

• Brand

• Color

• Weather/temp.

• Condition

• Remember that strikethrough marks are better than white out because it shows history

Sketches

• The rough and finished sketch should have the same information, but finished sketches are done to scale and have a legend/key

• A cross projection sketch represents all surfaces

What photos should be taken at a scene?

• Overall scene

• Items up close

• Different angles

• Different filters (especially for fluorescent reagents to detect other evidence)

• Always include a SCALE

• Capture transient details first (anything liable to change quickly in the scene)

Relevant Items

• Things connected to the incident or to the people/places/objects associated with the incident

Background Items

• Something not related to the incident, but simply a part of the natural/normal environment

Relevant Background Items

• Not directly related to the incident, but needed as a control/reference sample to compare back to other evidence or to corroborate/refute an alibi

• Ex. Arsenic in soil → Graveyard soil would be relevant background item

Search Patterns

• Strip/line

• Grid

• Spiral

• Wheel/ray

• Quadrant/zone

Goals of packaging evidence

• To prevent inadvertent (unintentional) change

  • Contamination - transfer of material from one piece of evidence to another piece of evidence, Locard’s Exchange Principle

  • Physical damage - breaking, phase change (melting, evaporating)

  • Chemical damage - anything that changes molecular bonding (oxidation, UV light, heat)

  • Biological damage - microbial growth/decomposition → bacteria/fungi break bonds and add DNA

• To prevent intentional tampering

• Volatile (easily evaporating) items go in metal air-tight paint can 

• For wet biological samples, swab and then let item dry before putting into a paper bag/box to allow air flow

Goals of handling evidence

• Maintain chain of custody

• Store and transport evidence in climate controlled conditions

Chain of Custody

• Overlapping log of who had possession of the evidence item at each point between crime scene and courtroom

  • Secured through evidence tape, sign in/out logs, and locked storage locations

Forensic Science

• Science applied to matters of law

• Establishes the facts of the crime - who, when, where, what, why, how

• Corroborates (verifies) the accuracy of testimonial evidence

• May be able to confirm what something is, but now always how it came to be there

Criminal Law vs. Civil Law

• Criminal Law

  • Regulates society as a whole (government represents society)

  • Suit initiated by prosecution

  • Penalties: jail, parole, probation, prison, community service, house arrest, fines

  • The prosecutor must prove guilt beyond a reasonable doubt

  • Cases: murder, terrorism, robbery, assault, kidnapping, battery

• Civil Law

  • Regulates disputes between individuals and/or companies

  • Suit initiated by plaintiff

  • Penalties: fines/restitution/remediation, punitive damages/punishment

  • The plaintiff must prove by the preponderance of the evidence (that it’s more likely than not) and defendant will be found liable

  • Cases: fraud, divorce, money laundering, child custody, embezzlement, car collision

Physical vs. Testimonial Evidence

• Physical Evidence: Tangible material that can assist the trier of fact in understanding events in question and relationship of people to events in question

• Testimonial Evidence: A statement made by a witness, either orally or in writing, that is presented in court as proof of a claim

Sources of inaccuracy/vulnerability in testimonial evidence

• People are not reliable recorders/reporters of events because the brain is constructive, adding and changing details, and many of those details are filtered through our own personal experiences and biases

• Stress, medical conditions, medications, drugs, trauma, lying, and word choice of investigators can influence testimony 

Unknown vs. Known samples

• Unknown (questioned/crime scene)

  • Items that were “happened upon” in the process of investigating the event

  • Their origin is not clear or certain or proven

  • Ex. blood, shoe print, hair strands

• Known (reference/standard/control)

  • Item collected/sought out/looked up on purpose from its original source, in order to compare the unknown back to it to establish the origin of the unknown

  • Ex. DNA swab from original source

Locard Exchange Principle

• Every contact leaves a trace 

• Establishes linkage

7 ways that Physical Evidence can be used

• Identify - What is it?

  • Compare back to a known reference library of drug chemicals and formulations

• Comparison - From where did the material originate?

  • Put 2 samples (usually a known and an unknown) side by side to compare their features/molecules present and absent, quantities of molecules, location/position 

  • Can result in Dissociation, Individualization, Classification

• Linkage - Evidence that shows 2 items were in contact with one another

  • Based on the Locard Exchange Principle

• Corroborate - Testimonial evidence of a witness, victim, suspect

  • Can verify/support or refute/disprove claims

• Reconstruct/Reenact - How did the events take place? Where? What position? When? In what order?

  • Ex. GPS history, camera footage, blood spatter, blood trajectories

• Establish M.O. - How a crime is committed/mode of operations

  • Most useful for repeated crimes

  • Useful to warn the public or link seemingly unrelated crimes

• Investigative Lead - Last resort of what to do it evidence and shows who/where to go next for more information

Individualization vs. Classification

• Individualization: As close to 100% certain as a scientist would ever say, that the 2 samples almost definitely did come from the same origin/source

  • DNA, unique tool marks

• Classification: It is possible, but not certain, that the 2 samples came from the same origin/source; this source can’t be ruled out as a possibility

  • It can narrow down to a specific group of people or smaller subset of possibilities

  • Shed hair, blood type, shoe print, any manufactured product

Disassociation

• These 2 samples (a known and unknown) could not have come from the same origin

• Can rule out suspects and saves time, money, and resources

Jigsaw Fit

• Can be used to individualize paper, clothing, glass, egg shells

Why scientists do not use “match”

• “Match” assumes individualization

Legal Precedent

• Legal standard/what has been decided in the past

Frye v. United States

• Defendant takes and passes a polygraph test claiming innocence but trial court excludes this from being admitted

• Defendant is convicted and appeals the conviction

• The Court of Appeals of the District of Columbia upholds the ruling

  • Scientific evidence must be “sufficiently established to have gained general acceptance in the particular field in which it belongs” to be admitted into court

Daubert v. Merrell

• It was alleged that a drug used to treat morning sickness, Bendectin, was causing birth defects (it was acting as a teratogen)

• The manufacturer of the drug (defendant) presented an expert witness who said none of existing scientific literature supported a cause-effect relationship

• Plaintiffs presented other expert witnesses who cited non-published/non-peer reviewed data and new analyses of previously published data to support a cause-effect relationship

• Lower court ruled plaintiff evidence inadmissible

• Daubert appealed to the Supreme Court 

• Supreme Court upheld the ruling but laid out the Daubert Standard

Daubert Standard

• Evidence must be relevant to the case

• The judge is the gatekeeper of what evidence is allowed in or not

• Evidence must be grounded in scientific knowledge, gained through reliable methods:

  • Tested technique, verifiable by others

  • Peer-reviewed/published

  • Known or potential error rate

  • Standardized protocol/threshold for conclusions

  • Widespread acceptance (Frye)

Kumho Tire Co. v. Carmichael

• Carmichael sued Kumho when a tire blew out and killed 1 person and injured more

• Plaintiff’s expert witness confirmed the blow out was a result of a defect

• Court ruled this evidence inadmissible because his methodology didn’t meet the Daubert standard

• Confirmed that people with technological expertise/experience can serve as an expert witness, but methods they use must still meet the Daubert Standard

Graphology vs. Handwriting Comparison

• Graphology: The study of handwriting to interpret personality traits

• Handwriting Comparison: Used to compare writing samples to determine who wrote something

• Both very unreliable!!!

  • But handwriting comparison is still allowed to be admitted into evidence in some places

Deductive vs. Inductive/Empirical reasoning

• Deductive Reasoning: Using a known principle (e.g., "all suspects with this DNA are excluded") to reach a certain conclusion about a specific suspect

  • General → Specific

• Inductive/Empirical Reasoning: Observing multiple similar crime scenes to form a broader theory that a single person committed them

  • Specific → General

First Documented Uses of Fingerprints

• To certify business transactions and sign important documents in China, Japan, and Babylon

• Used as personal identifiers

Anthropometry

• A system used to identify a person based on measurements of body parts and other features

• Aka “Bertillonage” system → Included 13 different measurements

• Less reliable than other methods

  • People can have the same set of measurements

  • Measurements can change

  • Body measurements aren’t left at a crime scene typically

  • Requires very standardized measurement techniques

Proof of Principle - Leavenworth Prison

• Will West was a man accused of being a repeat offender because someone with the name of William West had almost the same set of body measurements as him

• His incarceration at Leavenworth Prison was a “proof of principle” because fingerprints were what differentiated the 2 men

When are fingerprints formed in humans?

• The third to sixth month of fetal development

Biological function of fingerprints

• They enhance grip, improve touch sensitivity, and increase skin elasticity

Where in the skin do fingerprints originate from?

• Between epidermis and dermis

• Dermal papillae

Why and how can fingerprints be eroded/altered?

• Naturally

  • Aging

  • Injury

  • Medical conditions

  • Environmental factors

  • Medications

• Purposefully

  • Deep cuts

  • Burns

  • Abrasions

  • Skin grafts

• There needs to be 1-2 mm of damage to completely get rid of prints

Challenges to fingerprint evidence admissibility in court

• The process of fingerprint comparison wasn’t standardized enough to meet the Daubert Standard

• It hasn’t been proven that fingerprints are individual to a person

• Fingerprints are admissible in court and are generally accepted as reliable, though

Loops

• 60-65%

• Ridges that enter from 1 side, make a u-turn, and exit from the same side they entered

• 1 delta

• Includes radial and ulnar loops

Whorls

• 30-35%

• Ridges that form a circular shape, wrapping around fully circular or spiral

• 2 deltas

• Includes plain whorl, central pocket whorl, double loop whorl, and accidental whorl

Arches

• 5%

• Ridges enter from one side and leave the opposite side without any doubling back/circling

• 0 deltas

• Includes plain and tented arch

Radial Loops

• Looped ridges enter and exit on the side of the finger closest to the thumb

Ulnar Loops

• Looped ridges enter and exit on the side of the finger closest to the pinky

Plain whorl

• Circular ridges go below the line connecting the 2 deltas

Central Pocket Whorl

• Circular ridges remain above the line connecting the deltas

Double Loop Whorl

• Intertwined loop shapes (makes an S shape)

Accidental Whorl

• A combination of different types

Plain Arch

• Not a sharp angle

Tented Arch

• Steep/sharp angle to the ridges

Henry System of Classification

• If it’s a whorl, it gets points. If not, it doesn’t get points

• R. Index / R. Thumb + R. Ring / R. Middle + L. Thumb / R. Little + L. Middle / L. Index + L. Little / L. Ring + 1 / 1

  • Remember that the R. Thumb is the first one on the bottom because most people are righties and the thumb is the closest finger to the bottom/ground

• Point values are like a bracket

  • 16 / 16 + 8 / 8 + 4 / 4 + 2 / 2 + 1 /1 + 1 / 1

How to individualize a print

• Find the same 12-16 points of ridge details in the same relative locations on both the unknown and known prints

• Always begin with the unknown print!

Ridge Characteristics/Minutiae

Latent fingerprint residue components

• Water (98.5%)

• Solids (1.5%)

  • Organic (1%) → carbon, hydrogen, oxygen, nitrogen

    • Fatty acids, amino acids, glucose, lactic acid, isoagglutinogen, ammonia, urea

  • Inorganic (0.5%)

    • Cations (+) → Na+, Ca++, K+

    • Anions (-) → Cl-, CO3 -2, PO4 -3

Types of fingerprints left on surfaces

• Patent print → Fingerprints on hard surfaces which are visible (can be photographed without the aid of chemicals)

• Latent print → Fingerprints made by the body’s oils and sweat remaining on hard surfaces after contact (not visible)

• Plastic print → Three-dimensional fingerprints left on soft surfaces such as wax or wet paint (can be photographed without the use of additional techniques)

Approaches for the detection of latent prints

• Physical → mechanically pushing material against ridge

• Chemical→ create bonds

• Light-based → alone or in conjunction with a chemical method

Powders used for fingerprint detection

• Standard powder dusting

  • Mechanically adheres fine powder particles to the natural oils and moisture left behind by ridges of latent fingerprints, resulting in a visible ridge pattern on the surface. The color of the resulting print is the same color as the powder used (typically, a black or neon colored powder is used). The contrast of colored powder stuck to the ridge oils, as compared to the surface should result in a visible ridge pattern.

• Magnetic powder dusting

  • Uses a non-contact wand and magnetic powder to adhere powder to the surface and print. Fingerprint powders are ideal for smooth, nonporous surfaces like glass, plastic, and wood. This ensures powder will not be absorbed by the surface, will not absorb the fingerprint’s natural oils, and will not gather in surface indentations.

How to get the most complete, clear ink print

• Don’t press too hard or too light

• Do a complete roll from one side of the fingernail to the other

• Don’t roll the finger over multiple times

How to dust and lift latent prints most effectively

• Apply the powder gently with a brush or magnetic wand, develop the print until just visible, and photograph it

Chemical Detection Techniques

• Ninhydrin: Reacts with amino acids in prints to produce purple (Ruhemann's purple) marks, ideal for porous surfaces like paper

• Iodine Fuming: Iodine vapor reacts with fatty oils in prints, temporarily staining them brown/yellow; useful for porous items but requires immediate photography as prints fade

• Cyanoacrylate Fuming: Vapors bond to print residue (oils/moisture) on non-porous items (glass, metal), hardening them for subsequent powder or dye application, providing enhanced contrast

How to reveal latent prints using chemical methods properly

• Always cover fumes to avoid inhaling chemicals

• Process items in the proper sequence (e.g., chemical treatment before dusting)

• Photograph all developed prints before lifting or further processing.

Surfaces and their appropriate techniques

• Porous surfaces (e.g., paper, cardboard, raw wood) absorb water and water-soluble components (amino acids) from the sweat within minutes

  • Ninhydrin technique should be used

• Non-porous surfaces (e.g., glass, plastic, metal, rubber) do not absorb residue; the print remains on the outermost surface

  • Powder dusting and super glue fuming

• Semi-porous surfaces (e.g., glossy magazines, waxed paper, varnished wood) both absorb and resist residue, requiring a hybrid approach

What variables may influence the success of recovering a latent print?

• Environmental factors (humidity, temperature, air, light), the surface type (porous/non-porous, texture), the deposition dynamics (pressure, duration, cleanliness of the finger), and the time elapsed

Standards for concluding prints to be an individualization

• There is not a specific minimum minutiae count in the U.S. It depends on the size and quality of the Unknown print and is left up to the examiner's discretion

ACE-V process

• Analysis- Is this latent print of high enough quality to even begin a comparison?

• Comparison- The Unknown and Known side-by-side, looking for features of the Unknown found in the Known

• Evaluation- Conclusion based on comparison above; examiner is always starting from a position of trying to show an exclusion

• Verification- Another examiner repeats the full ACE process

The three possible conclusions a fingerprint examiner can reach following a comparison

• Individualization, Exclusion, Inconclusive

Blind Verification

• The examiner performing the Verification should be "blind" and have no knowledge of the first examiner's Conclusion.

How is the error rate in fingerprint comparison calculated?

• Can not be done in a real case

• Fake cases put into lab work that fingerprint examiners do to test if the examiners are doing their work well

• Error Rate = [the number of incorrect conclusions made by the examiner]/[the total number of mock cases processed]

What is the difference between a false positive and a false negative in fingerprint comparison?

• False negative - The examiner said that it was an exclusion, but it wasn’t

• False positive - The examiner said that it was an identification, but it wasn’t

• False Positive Error Rate = [the number of incorrect Individualizations made by the examiner]/[the total number of mock cases processed]

• False Negative Error Rate = [the number of incorrect Exclusions made by the examiner]/[the total number of mock cases processed]

Brandon Mayfield Case

• Brandon Mayfield is an American lawyer who was incorrectly detained in connection with the 2004 Madrid train bombings on the basis of a faulty fingerprint match

• Mayfield's case underscored the need for rigorous scrutiny of forensic evidence in legal proceedings. It prompted discussions on the limitations of fingerprint analysis and the potential for errors, impacting how such evidence is presented in court