Forensic Science: Evidence Types, Crime Scene Procedures, and Analysis Techniques

What forensic principle explains why soil can transfer from a crime scene to a suspect?

Locard's Exchange Principle

Why is blood type considered class evidence instead of individual evidence?

Many people share the same blood type

What distinguishes class evidence from individual evidence?

Class evidence groups; individual evidence identifies a single source

Why is physical evidence generally more reliable than eyewitness testimony?

It is objective and measurable

What is circumstantial evidence, and how can it still be strong in court?

Indirect evidence that implies a fact and can still be powerful with support

What is the overall purpose of forensic science in the legal system?

To apply science to legal questions and investigations

How does secondary transfer differ from primary transfer?

Secondary transfer occurs through an intermediary

Why is chain of custody critical to evidence admissibility?

It ensures evidence integrity

Why is class evidence still valuable even though it cannot identify a single person?

It narrows suspect pools

What makes fiber evidence circumstantial rather than direct?

It does not directly prove guilt

What is the very first responsibility of the first officer at a crime scene?

Secure the scene

What are the four most basic methods of crime scene documentation?

Photos, video, sketches, notes

Why must wet, or blood biological evidence never be placed in plastic bags?

It traps moisture and causes mold/bacteria growth

Why must charred debris be stored in airtight containers?

It preserves accelerants

Why should blood-stained clothing be packaged separately in paper bags?

Prevents cross-contamination

Why are fingernail scrapings considered important trace evidence?

They may contain attacker's DNA

How do crime scene sketches help investigators after evidence has been removed?

They show the original layout

What type of evidence might be found at a hit-and-run scene?

Glass, paint, fibers

Why must bystanders be kept away from a crime scene?

To prevent contamination

What determines success in recognizing and collecting physical evidence?

Skill of investigators

What substance makes latent fingerprints invisible to the naked eye?

Sweat and oils

What type of fingerprint is left in soft material like clay or wax?

Plastic print

What does cyanoacrylate (superglue) fuming reveal on a fingerprint?

White polymer ridges

What can be determined from a fingerprint with only a loop pattern and no minutiae?

Only class characteristics

How many points of comparison are commonly required for fingerprint identification in court?

12 points

What does a shoeprint with unique cuts and wear indicate?

Individual evidence

What does a shoeprint that matches only tread and size reveal?

Class evidence

What kind of information does track width provide in vehicle analysis?

Vehicle class

What type of tire mark is created when a car tries to turn while braking?

Yaw mark

What do long, dark tire marks usually indicate?

Sudden braking or acceleration

Why can a hair without a root not provide nuclear DNA?

No follicle = no nuclear DNA

Why is hair useful for long-term drug detection?

Drugs become trapped inside growing hair

What does a stretched hair root with tissue attached indicate?

Forceful removal

What does a club-shaped root without damage indicate?

Natural shedding

What hair layer contains pigment granules?

Cortex

Which hair structure is examined when overlapping scale patterns are observed?

Cuticle

Why must keratin be dissolved before toxicology testing of hair?

To break down keratin and release any trapped drug analytes so they can be extracted and detected. 

What does a flattened hair cross-section indicate about the hair?

Curl pattern

How can two hairs appear similar macroscopically but differ microscopically?

Different individuals

Why is pubic hair considered significant evidence?

It is coarse and unique

What finding most strongly indicates asphyxiation?

Petechial hemorrhaging

What causes cherry-red discoloration of a deceased body?

Carbon monoxide poisoning

What are defense wounds and where are they most commonly found?

Injuries on hands/arms

What bone is commonly fractured during strangulation?

Hyoid bone

What firearm discharge pattern causes stippling on skin?

Stippling

What evidence suggests postmortem body movement?

Blood pooling in multiple areas

Why is petechial hemorrhaging significant?

It indicates asphyxia

What is blunt force trauma describing: cause, manner, or mechanism of death?

Cause of death

What specialist identifies poisons in body tissues?

Toxicologist

What type of death is a recreational drug overdose classified as?

Accidental

What is the best internal location for measuring body temperature after death?

Liver

What does algor mortis describe?

Cooling of body

What does rigor mortis indicate about the body?

Stiffening of muscles

What does livor mortis show investigators?

Blood pooling after death

What stage of decomposition shows skin discoloration and bloating?

Bloat stage

What two biological processes cause decomposition?

Autolysis and putrefaction

Which insect is usually the first to arrive at a dead body?

Blow fly

What does forensic entomology help determine most accurately?

Time since death

Why do anthropology and entomology often work together?

They assist with identity and time of death

What factors influence how fast a body cools after death?

Temperature, environment, body size

What qualifications must a medical examiner possess?

Medical degree and board certification

What procedure is used when cause of death cannot be determined by observation?

Autopsy

What body part is often bagged to preserve trace evidence?

Hands

What are the five manners of death?

Homicide, suicide, accident, natural, undetermined

Which manner of death applies when one person intentionally kills another?

Homicide

What manner of death is chronic alcoholism usually ruled as?

Natural

Which of the following is NOT a manner of death: accident, suicide, natural, drowning?

Drowning

What is adipocere and how long does it usually take to develop?

Waxy fat forms on decomposing body; ~8-12 weeks

What method can be used to estimate time of death using eye fluid?

Potassium levels

What does soot and Co2 in the lungs indicate?

Victim was alive during fire

Which forensic specialist evaluates a suspect's mental competence?

Forensic psychiatrist

What does a forensic anthropologist help reconstruct for identification?

Facial reconstruction

What forensic database stores fingerprint records?

AFIS

What does CODIS stand for and what type of data does it store?

Combined DNA Index System; DNA profiles

Why are forensic databases important to modern criminal investigations?

They allow rapid database comparisons