forensics!

Forensic Science

The application of scientific methods and techniques to investigate crimes and examine evidence for use in court

Three reasons crime labs have increased

Population growth increase in crime rates and advances in science and technology

Seven basic services of a crime lab

Physical Science Biology Firearms Toxicology Latent Fingerprints Computer Forensics Evidence Collection

Physical Science Unit

Analyzes drugs glass paint explosives and other chemicals

Biology Unit

Analyzes biological evidence such as blood saliva hair and DNA

Firearms Unit

Examines firearms bullets cartridge cases and gunshot residue

Toxicology Unit

Analyzes drugs poisons and alcohol in blood and body fluids

Latent Fingerprint Unit

Develops and analyzes latent fingerprints

Computer Forensics Unit

Examines digital evidence such as computers phones and electronic data

Evidence Collection Unit

Collects and preserves physical evidence at crime scenes

Role of a forensic scientist

Analyzes evidence interprets results and may testify as an expert witness in court

Expert witness

A specialist allowed to give opinions in court based on training and experience

Frye Standard

Scientific evidence must be generally accepted by the scientific community

Daubert Criteria

Evidence must be testable peer reviewed have known error rates and be widely accepted

Sir Arthur Conan Doyle contribution

Popularized scientific crime solving through Sherlock Holmes

Sherlock Holmes impact

Promoted logical reasoning observation and forensic techniques

Hans Gross contribution

Founded criminalistics and emphasized scientific methods in investigations

Alphonse Bertillon contribution

Developed anthropometry and standardized crime scene photography

Francis Galton contribution

Advanced fingerprint classification and individuality

Edmond Locard contribution

Proposed Locard’s Exchange Principle

Locard’s Exchange Principle

Every contact leaves a trace

Physical Evidence

Any object or material that can establish that a crime occurred or link a suspect to a crime

Responsibilities of first officer

Secure scene ensure safety provide medical aid detain suspects preserve evidence

First step at a crime scene

Secure and isolate the scene

Crime scene documentation

Notes photographs sketches and videos

Crime scene notes

Written record of observations and actions taken

Crime scene photographs

Capture scene before evidence is moved

Crime scene sketches

Show layout measurements and evidence placement

Systematic crime scene search

Organized method to locate evidence

Search patterns

Line grid spiral zone quadrant

Evidence collection steps

Locate document collect package label seal and log

Packaging dry evidence

Use paper bags or envelopes

Packaging wet or biological evidence

Air dry then package in breathable containers

Airtight containers used for

Liquids volatile substances and arson evidence

Chain of custody

Documented record of who handled evidence from collection to court

Purpose of chain of custody

Ensures evidence integrity and admissibility

Common types of physical evidence

Blood hair fibers fingerprints weapons drugs glass soil

Identification of evidence

Determining what an item is

Comparison of evidence

Determining whether two items share a common origin

Class characteristics

Traits shared by a group such as blood type

Individual characteristics

Traits unique to a single source such as DNA profile

Value of class evidence

Narrows suspect pool and supports investigations

NIBIN

National Integrated Ballistic Information Network that links firearms evidence

CODIS

Combined DNA Index System that compares DNA profiles

AFIS

Automated Fingerprint Identification System that matches fingerprints

Ridge characteristics minutiae

Ridge endings bifurcations dots islands enclosures

Three fingerprint patterns

Loop whorl arch

Visible fingerprints

Made by blood ink or dirt

Plastic fingerprints

Made in soft materials like wax or clay

Latent fingerprints

Invisible prints left by sweat and oils

AFIS definition

Computer system that stores and compares fingerprint data

Developing prints on porous surfaces

Iodine fuming and ninhydrin

Developing prints on nonporous surfaces

Powder dusting and cyanoacrylate

Preserving latent fingerprints

Photograph lift with tape and mount on backing card

Ten print card

Standard fingerprint record of all ten fingers

Fingerprint comparison

Matching minutiae patterns between prints

Forensic pathologist role

Determines cause and manner of death through autopsy

External autopsy

Examines body surface for injuries and identifying features

Internal autopsy

Examines organs for trauma or disease

Toxicology phase

Tests bodily fluids for drugs or poisons

Cause of death

The injury or disease that led to death

Manner of death

Natural accident suicide homicide or undetermined

Common causes of death

Trauma disease poisoning suffocation

Livor Mortis

Settling of blood after death appearing within 30 minutes to 2 hours and fixed after 8 to 12 hours

Rigor Mortis

Muscle stiffening beginning 2 to 6 hours peaking at 12 hours and disappearing after about 36 hours

Algor Mortis

Cooling of the body after death

Forensic anthropologist role

Analyzes skeletal remains

Determining sex from bones

Pelvis and skull features

Determining age from bones

Growth plates teeth and bone degeneration

Determining race from bones

Skull shape and facial features

Forensic entomologist role

Studies insects on a body to estimate time of death

Insect life cycles

Used to determine postmortem interval

Physical dependence

Body adapts to a drug and experiences withdrawal

Psychological dependence

Emotional or mental reliance on a drug

MDMA classification

Stimulant and hallucinogen

Methamphetamines

Powerful stimulants

Rohypnol

Central nervous system depressant

THC

Psychoactive compound in marijuana

Methadone

Opioid used for pain management and addiction treatment

Cocaine

Powerful stimulant

Oxycontin

Prescription opioid painkiller

Controlled Substances Act

Law regulating drug manufacture distribution and use

Drug schedules

Classification from Schedule I to V based on abuse potential and medical use

Field sobriety tests

Walk and turn one leg stand and horizontal gaze nystagmus

Forensic toxicologist role

Identifies drugs and poisons in the body

Alexander Gettler contribution

Developed forensic toxicology methods

Charles Norris contribution

Improved death investigations in New York City

Prohibition poisoning cases

Lead radium arsenic cyanide carbon monoxide and poisoned alcohol

Importance of Gettler and Norris cases

Exposed dangers of poisons influenced public policy and improved forensic science