Criminal Inv-Chapter 5, Laboratory and Technical Serv Flashcards
trustworthiness of an expert is important to the net worth of the ___ _____
entire investigation
Any suspicion of subjectivity or dishonesty destroys the legal significant of evidence
becuase the average trier of facts may easlily view such conduct as affecting the credibility of the entire investigation
criminalistics
is the profession and scientific discipline directed to the recognition, identification, individualization and evaluation of physical evidence by application of the naturla sciences in matters of law and science
identification in criminalistics is aligned with the logic of __
set theory- all objects can be divided and subdivided into various sets on the basis of their properties. identification in relation to physical evidence and its analysis is defined as the determination of some set to which an object or substance belongs
primary carrier of genetic information in living organisms, consists of a long, spiral structure that has been likened to a twisted ladder
molecule of DNA
handrails of the ladder string together to form the ladder rungs. Each rung consists of a
base pair- two of four varieties of nucleic acid and are combined in pairs called nucleotides
the sequence of these base pairs constitutes the genetic coding of
DNA
DNA in humans is found in all cells that contain a nucleus- except
red blood cell
Each nucleated cell usually contain a full complement of an individuals DNA called __
genome
Genome consists of approx how many base pairs? of which about ____actually differ from person to person
3 billion base pairs
3 million
person-to-person differences within a particular segment of DNA sequence ar referred to as
alleles
polymerase chain reaction -PCR
extracting DNA from small evidence sample and then replicating it thru a complex operation of repeated heating and cooling cycles and exposure to an enzyme. Each cyle doubles the quantity of DNA. by examining several locations (loci) where variations occurs, a typing profile can be produced
Short tandem repeats-STR
FBI has selected thirteen STR loci to serve as a standard battery of core loci,
According to standard PCR protocol. Each dark spot that appears can be read as “yes” or
“no” to the question of whether a particular individual possesses a given
allele
a difference of a single allele can exclude someone as the donor of that evidence sample. the more locations that show the same allele pattern, the stronger the evidence that the two samples came from the same individual
allele
DNA is found in
all body tissues and fluids, saliva, skin cells, bone, teeth, tissue, urine, feces and host of other biological specimens.
DNA molecule is long lived, it is likely to be detectable for many years in bones and body fluids stains from older criminal cases
DNA
human cell contains two tpes of DNA.
nuclear and mitochondrial
nuclear DNA
contains 23 pairs of chromosomes in the nuclei of the cells and each parent contributes to the genetic makeup of the chromosomes
Mitochondrial DNA-mtDNA
is found outside the nucleus and is inherited soley from the mother. there are hundred of thousands of mitochondria copies in human cell compared to just one nuclear DNA located in the same cell
Scientist use mtDNA to identify subject when
nuclear DNA is significantly degraded, such as charred remains.
mtDNA is more vigorous, time consuming and costly than nuclear DNA profiling
only a handful of forensic labs process evidence for mtDNA determinations
spectrography
the radiation from incandescent gas or vapor is concentrated in certain discrete wavelengths. It will produce a complete elementary analysis of evidence sample containing mineral and other inorganic compounds. it is an all-purpose intrument for criminalistics
chromatography
method of separating compounds to identify the components. such as illegal drugs or poison
Gas chromatographs
analytical tool becuase with them microsamples of such complex compositions as gasoline, fuel oil, perfumes, hair dressings and paint thinners can be identified from their constituents
X-ray crystallography
identifing of any crystalline solid or compound from which a crystalline sold derivative can be made
X-ray diffraction
used in proccesing very small samples in examining samples with noncrystalline impurities and identifying inorganic and mineral substances
X-ray spectra
used for analysis and identification
neutron activation analysis-NAA
can analyze samples one hunderd times to small for ordinary spectrographic techniques.
gamma-ray-spectrometer
to measure the distinctive radioactive gamma-ray emissions and thereby to identify elements from which the rays originate.
NAA technique and its application in the study of gunshot residues have returned a potential item of evidence to investigators.
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paraffin-lifing kits are used on suspects hands and NAA measurments for the presence of
antimony and barium, which are common gunshot residues,
trace metal detection technique-TMDT
distinctive signatures of handguns, tools and other metal objects .
ultrasonic cavitation
etching method used for restoring obliterated serial numbers on firearms and other metal objects
lasers
used in detection of latent fingerprints and of questioned documents.
voiceprinting
identification of voices.
crytography
use of simple ciphers and codes to protect the security of messages
substitution cipher
most common cipher used.
transposition ciphers
change in the order of the enciphered material
reversal transposition
reversed numbers
split combination
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National Integrated Ballistic Information Network-NIBIN
maintained by ATF. database on fired cartridge casings, bullets, shotgun shells.
International Forensic Automotive Paint Data Query-PDQ
developed and maintained by Forensic Laboratory Services of the Royal Canadian Mounted Police. Database contains chemical and color info pertaining to factory auto paint and can determine make,model,year and assembly plant on more than 13000 vehicles. Contributors to database include Canada, US as well as 21 other countries.
Shoeprint Image Capture and Retrieval-SICAR
shoe sole database
