MMSC220 Exam #1

term that can be used interchangably with forensics/forensic scientist

criminalistics/criminalist

true or false: forensic science is a branch of law enforcement

false

true or false: forensic scientists do not usually go to investigate crime scenes or interrogate suspects

true

main functions of forensic scientists

to analyze physical evidence and testify in courtroom

expert testimony

possesses particular skill or has knowledge in a trade or profession that will aid  the court in determining the truth of a matter at issue  

AAFS

American Academy of Forensic Sciences

professional organization w/ 11 sections 

MAAFS

local organization

Mid Atlantic Association of Forensic Scientists

def of forensic toxicology

forensic discipline

analyses of bodily specimens (fluids and tissues) fot chemicals such as alcohols, illicit drugs, medications, poisons, and metals

DNA analysis/profiling

area of forensic science

comparing DNA samples from different locations and determining the probabilityof matches

analysis of seized drugs

area of forensic science

analysis of suspected illicit and controlled substances

forensic pathology

area of forensic science

ID of deceased

determining TOD, mechanism of death, COD, manner of death (MOD)

cause of death

immediate reason of event that precipitates death

etiologically specific disease or injury that resulted in death

ex. heart attack, blunt force, drug toxicity

manner of death 

goes on death certificate

classification / categorization used for how the death came about

five categories:

1. Natural (only hospitals can certify)

2. Homicide

3. Suicide

4. Accident

5. Undetermined

forensic anthropology

area of forensic science

identification and examination of human skeletal reamins 

may reveal sex, race, presence of skeletal injuries 

forensic entomology

area of forensic science

study of insects in relation to a criminal investigation 

forensic odontology

area of forensic science

use characteristics of teeth, alignment, and overall structure

dentition

pertains to the development of teeth and their arrangement in the mouth.

unique to each person

odontograms

a medical record for dental patient

other areas of forensic science

fire/arson investigation, firearms/ballistics, fingerprints, forensic microbiology

examples of trace evidence

textile fibers, hairs, paint, etc.

carl scheele

created first test to detect arsenic in a corpse

mathieu orfila

created first treatise on detection of poisons and their effects on animals o “father of forensic toxicology”

alphonse bertillon

anthropology and morphology applied as a system of personal identification o “father of criminal identification” 

the bertillon system or bertillonage 

francis henry galton

first definitive study of fingerprints and methodology of classification, fingerpirnts 

sir arthur conan doyle

first novel with character Sherlock Holmes 

edmund locard

first police laboratory

____ exchange principle 

locards exchange principle

when two objects come in contact with one another, materials are exchanged between them

Sir Alec Jeffreys

developed first profiling test

what happened in 1923

the oldest crime lab in the US was established

International Organization for Standardization (ISO) 17025 

Laboratory accreditation  

whats involved in securing the crime scene

• Treat the scene as if the crime is still occurring  

• o Obtain medical attention if needed  

• o Law enforcement agents should never do anything to alter the crime scene  

types of crime documentation

Crime scene log, note taking, evidence markers, evidence log, sketches, photographs, and  video and/or audio recordings

three distances crime scene photos should be taken

 Overall or perspective views, Medium  (within 6 feet), and close-up (within 12 inches) 

methods of systematic search of crime scene

strip (or lane), spiral, and grid  

what is the crime scene investigators role?

collect physical evidence

common types of physical evidence

• Body fluids  

• Fingerprints – Visible and latent (hidden)  

• Hair  

• Drugs  

• Weapons  

• Impressions  

• Arson and bomb evidence  

trace evidence

materials transferred between people, objects, or the environment during a crime

questioned sample

ex. sample of blood

aka unknown sample

reference sample

ex. buccal swab

aka known sample

true or false: reference sample is compared with unkown sample

true

substrate/control samples

clean samples of the collection materials or unstained portions of the material the biological evidence is deposited on

used to protect evidence and prevent mold growth

brown paper bag

goal for handling evidence

to prevent changes in physical evidence

why are DNA tests prone to contaimination

high sensitivity

in evidence collection, there must be evidential value of

demonstrating transfer between victim and suspect (aka locards exchange principle)

who are victims of assault examined by

sexual assault nurse examiner or forensic nurse examiner

4th amendment

protects people from unreasonable searches and seizures by the government.

chain of custody

a recorded means of verifying where the evidence has travelled and who handled it before the trial

all those who examined evidence may need to testify in court

where is evidnece usually submitted?

in person

forensic pathologist

Specialist doctor who performs autopsies

medical examiner

Forensic pathologist with legal authority

coroner

Government official, not always a doctor

clinical autopsy

extent of disease for which doctor was treating patient

need consent from family

medical-legal (forensic) autopsy

investigation of sudden, suspicious, accidental, unnatural or unusual deaths

goals of autopsy

• Positive identification of body

• COD and MOD

• TOD (most controversial)
  External and internal abnormalities

• External and internal injuries

  • Photos for evidence

  • Full written report of findings

• Toxicology, histology samples

external examination

• Identifying information:

  • Sex, age, race (estimated), body weight/height

  • Tattoos, scars, birthmarks

• Condition of the body:

  • Signs of decomposition, livor mortis (postmortem lividity), rigor mortis

• Clothing and belongings:

  • Documented and examined for blood, tears, gunshot residue, etc.

• Injuries or marks:

  • Bruises, abrasions, lacerations, gunshot wounds, stab wounds, needle marks, burns

• Evidence collection:

  • Fingernail scrapings

  • Hair, fibers, or trace evidence

  • Swabs for DNA or sexual assault kits

internal examination

• Y shaped incision

• Exposure of internal organs 

• Organs are weighed + retained in formalin for histology and microscopic examination

first step of comparision

properties of the two specimens, questioned/unknown and exemplar/known/reference,  are selected for comparison 

second step of comparision

draw conclusion—do they or don’t they come from the same source?

associative evidence

evidnece that links two separate entities

class characteristics

• Properties of physical evidence might only be associated with a group (common source)

• not a single source

• Ex. abo blood group system

  • Product rule helps determine if characteristic is significant

individual characteristics

•  Properties of evidence that can be attributed to a common source with an extremely high degree of certainty (probability)

  • Mathematical certainty is not possible (cannot state w 100% certainty that two specimens have same soruce)

exclusion evidence

physical evidence can exclude (rule out or exonerate) an individual as contributor

postmortem interval (PMI)

 approximating time of death 

def of rigor mortis

stiffening of muscles after death 

how long does rigor mortis take and last

Begins within 24 hours and disappears within 36 hours

def of livor mortis

• postmortem lividity  

• Pooling of blood to the lowest point

how long does livor mortis take and last

Begins immediately after death and continues for up to 12 hours

def of algor mortis

body temperature cools until it reaches ambient temperature

how long does algo mortis take

about 30 hours

first insect to generally infest a body

blow flies

each stage of life for a blow fly is called

instars 

__ helps determine time of death in entomology

sucession of arrival

def of endomotoxicology

helps determine COD w/ bioaccumulation in the food chain (ex. Maggots grow faster when feeding on body w/ cocaine)

life cycle of a blow fly: stage one

Eggs laid around openings on the decedent such as eyes and nose

life cycle of a blow fly: stage two

Eggs hatch into first-stage larvae (maggots) 

life cycle of a blow fly: stage three

Larvae feed and molt into second-stage maggots

life cycle of a blow fly: stage four

They feed more and molt into third-stage maggots

life cycle of a blow fly: stage five

They become pupae on the ground  

life cycle of a blow fly: stage six

 Adult blow flies emerge to begin the process again

insect involved in later waves of decomp

beetles

how is biological evidence (semen, vaginal fluid, saliva) preserved?

swab or Pasteur pipette and transfer to filter pape

positive control

should give positve result

negative control

should give negative result

type I error

False positive – negative that falsely reads positive  

MOST SERIOUS

type II error

False negative – positive that falsely reads negative  

less serious than type I

Preliminary/screening/presumptive tests 

Positive indicates blood might be present 

  Negative rules out blood  

preliminary tests are highly _ , _ and prone to

sensitive, qualitiative, false positives

confirmatory tests are typically

dne in the lab and have greater specificity

sensitivity

Probability that the presence of an analyte will give a positive result 

An assay’s ability to detect an analyte in samples 

specificity

probability that the absence of an analyte will give a negative result 

 An assay’s ability to correctly identify an analyte in a sample  

which contains nuclear DNA?

white blood cells

two parts of whole blood

cellular components (rbcs, wbcs, and platelets) and fluid portion (serum or plasma)

what do presumptive assays for blood rely on

oxidation reduction reactions catalyzed by the heme group (hemoglobin) of blood (oxidase activity)

what do presumptive assays for blood result in

color change or release in photon or flourescnece

Phenolphthalin assay (Kastle-Meyer test)

presumptive positive (purple pinkish)

detects possible presence of hemoglobin in blood

oxidase acitvity of hemoglobin catalyzes phnolphtalin oxidation

luminol

chemiluminescence

what could trigger false positivies

• Any strong oxidizing agent such as bleach and household cleaners  

• Any substance with peroxidase activity 

approx 20-30% of human proteins are

polymorphic (multiple alleles)