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analyst training > definitions (per SWGDAM & QAS) > Flashcards

definitions (per SWGDAM & QAS) Flashcards

1
Q

accreditation

A

the formal recognition that a laboratory meets or exceeds a list of standards, including the FBI’s QAS, to perform specific tests
accreditation is administered by a nonprofit professional association of persons actively involved in forensic science that is nationally recognized within the forensic science community in accordance with the provisions of the Federal DNA Identification Act or subsequent laws

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2
Q

allele

A

a form of a gene that is located at a specific location on a specific chromosome alleles targeted in STR analysis vary in length

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3
Q

analytical threshold

A

the minimum height requirement at and above which detected peaks can be reliably distinguished from background noise
peaks above this threshold are generally not considered noise and are either artifacts or true alleles

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4
Q

artifact

A

a non-allelic product of the amplification process (e.g., stutter, non-templated nucleotide addition, or other non-specific product), an anomaly of the detection process (e.g., pull-up or spike), or a by-product of primer synthesis (e.g., “dye blob”)

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5
Q

assumed contributor

A

an individual whose DNA on an item of evidence is reasonably expected

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6
Q

binary model/method

A

an interpretation scheme in which there are only two values (possible or not possible) for each decision (e.g., a peak is either “an allele” or “not an allele”; a genotype is “included” or “not included”)

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7
Q

composite profile

A

a DNA profile generated by combining typing results from different loci obtained from multiple injections of the same amplified sample and/or multiple amplifications of the same DNA extract
when separate extracts from different locations on a given evidentiary item are combined prior to amplification, the resultant DNA profile is not considered a composite profile

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8
Q

deduced profile

A

inference of an unknown contributor’s DNA profile after taking into consideration the contribution of a known/assumed contributor’s DNA profile based on quantitative peak height information

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9
Q

distinguishable mixture

A

a DNA mixture in which relative peak height ratios allow deconvolution of the profiles of major/minor contributor(s)

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10
Q

dropout

A

when one or more alleles present in a sample are not observed above the analytical threshold

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11
Q

evidence/questioned sample

A

biological sample recovered from a crime scene or collected from persons or objects associated with a crime

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12
Q

exclusion

A

a conclusion that eliminates an individual as a potential contributor of DNA obtained from an evidentiary item based on the comparison of known and questioned DNA profiles (or multiple questioned DNA profiles to each other)

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13
Q

exclusionary hypothesis

A

also referred to as Hd or H2; the term typically used in the denominator of the likelihood ratio to represent the defense hypothesis, which does not include the person of interest as a contributor to the DNA profile

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14
Q

genotype

A

results of autosomal STR analysis of an individual at one or more genetic loci

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15
Q

guidelines

A

a set of general principles used to provide directions and parameters for decision making

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16
Q

heterozygote

A

an individual having different alleles at a particular locus; usually manifested as two distinct peaks for a locus in an electropherogram

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17
Q

homozygote

A

an individual having the same (or indistinguishable) alleles at a particular locus; manifested as a single peak for a locus in an electropherogram

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18
Q

inclusion

A

a conclusion for which an individual cannot be excluded as a potential contributor of
DNA obtained from an evidentiary item based on the comparison of known and questioned DNA profiles (or multiple questioned DNA profiles to each other)

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19
Q

inclusionary hypothesis

A

also referred to as Hp or H1; the term typically used in the numerator of the likelihood ratio to represent the prosecution hypothesis, which includes the person of interest as a contributor to the DNA profile

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20
Q

inconclusive

A

a determination that no conclusion (i.e., inclusion/exclusion) can be drawn from the comparison of a reference sample to suitable data
this could also result from statistical analyses that fail to provide sufficient support for
an inclusion or exclusion

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21
Q

indistinguishable mixture

A

a DNA mixture in which relative peak height ratios are insufficient to attribute alleles to individual contributor(s)

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22
Q

intimate sample

A

a biological sample from an evidence item that is obtained directly from an individual’s body; it is not unexpected to detect that individual’s allele(s) in the DNA typing results

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23
Q

known sample

A

biological material for which the identity of the donor is established and used for comparison purposes

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24
Q

likelihood ratio (LR)

A

the ratio of two probabilities of the same event under different and mutually exclusive hypotheses
typically the numerator contains the prosecution’s hypothesis and the denominator the defense’s hypothesis

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25
Q

locus

A

the specific physical location of a gene on a chromosome
in forensic DNA analysis, it refers to the specific sites being tested

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26
Q

major contributor(s)

A

an individual(s) who can account for the predominance of the DNA in a mixed profile

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27
Q

masked allele

A

an allele of the minor contributor that may not be readily distinguishable from the alleles of the major contributor or an artifact

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28
Q

minor contributor(s)

A

an individual(s) who can account for the lesser portion of the DNA in a mixed profile

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29
Q

mixture

A

a DNA typing result originating from two or more individuals

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30
Q

mixture ratio

A

the relative proportion of the DNA contributions of multiple individuals to a mixed DNA typing result, as determined by the use of quantitative peak height information
when expressed as a percentage it is termed a mixture proportion

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31
Q

noise

A

background signal detected by a data collection instrument

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32
Q

partial profile

A

a DNA profile for which complete typing results are not obtained at all tested loci due, for example, to DNA degradation, inhibition of amplification and/or low-quantity template

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33
Q

peak height ratio (PHR)

A

the relative proportion of two alleles at a given locus, as determined by dividing the peak height of an allele with a lower relative fluorescence unit (RFU) value by
the peak height of an allele with a higher RFU value, and then multiplying this value by 100 to express the PHR as a percentage
used as an indication of which alleles may be heterozygous pairs and also in mixture deconvolution

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34
Q

probabilistic genotyping

A

the use of biological modeling, statistical theory, computer algorithms, and probability distributions to calculate likelihood ratios (LRs) and/or infer genotypes for the DNA typing results of forensic samples

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35
Q

random match probability (RMP)

A

the probability of randomly selecting an unrelated individual from the population who could be a potential contributor to an evidentiary profile

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36
Q

restricted

A

referring to a statistical approach conditioned on the number of contributors and with consideration of quantitative peak height information and inference of contributor mixture ratios
used to limit the genotypic combinations of possible contributors

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37
Q

single-source profile

A

DNA typing results determined to originate from one individual based on peak height ratio assessments and the number of alleles at given loci

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38
Q

source attribution

A

a declaration which identifies an individual as the source of the DNA that produced an evidentiary single-source or deduced contributor profile
this statement is based on a statistical estimate that meets or exceeds a laboratory defined threshold

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39
Q

stochastic effects

A

the observation of intra-locus peak imbalance and/or allele drop-out resulting from random, disproportionate amplification of alleles in low-quantity template samples

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40
Q

stochastic threshold

A

the peak height value below which it is reasonable to assume that, at a given locus, allelic dropout of a sister allele in a heterozygous pair may have occurred

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41
Q

stutter

A

a minor peak typically observed one repeat unit smaller than a primary STR allele resulting from strand slippage during amplification

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42
Q

theta (θ)

A

a value used to adjust statistical calculations that rely on population databases to correct for substructure within populations

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43
Q

uninterpretable

A

the determination that DNA results at one or more loci cannot be interpreted due to poor or limited data quality

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44
Q

unrestricted

A

referring to a statistical approach performed without consideration of quantitative peak height information and inference of contributor mixture ratios

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45
Q

accuracy

A

the ability of a measurement to give results close to a true value

46
Q

administrative review

A

an evaluation of the report and supporting documentation for consistency with laboratory policies and for editorial correctness

47
Q

analyst

A

an employee or contract employee, that has successfully completed the laboratory’s training requirements for casework sample analysis, passed a competency test, and has entered into a proficiency testing program according to these standards
this individual can conduct and/or direct the analysis of forensic samples, interpret data, reach conclusions, and generate reports

48
Q

analytical control

A

a sample used to demonstrate that a method works correctly and to ensure the data are valid

49
Q

analytical documentation

A

the documentation of procedural notes, controls, and instruments used; observations made; results of tests performed; and charts, graphs, photos, and other documentation generated which are used to support the analyst’s conclusions

50
Q

analytical procedure

A

an orderly, step-by-step process designed to ensure operational uniformity and to minimize analytical drift

51
Q

annual

A

once per calendar year

52
Q

audit

A

an on-site inspection used to evaluate, confirm, and/or determine the extent to which specified requirements are fulfilled

53
Q

audit team

A

one or more individuals, including at least one auditor, that performs an
inspection of a laboratory
at least one audit team member shall be or have been an analyst previously qualified in the laboratory’s current DNA technologies and platforms

54
Q

auditor

A

an individual who has successfully completed the FBI’s DNA auditor training course

55
Q

biochemistry

A

the study of the nature of biologically important molecules in living systems, DNA replication and protein synthesis, and the quantitative and qualitative aspects
of cellular metabolism

56
Q

casework reference sample

A

biological material (e.g., buccal swab, fingerprick, or blood draw) obtained directly from a known individual and used for purposes of comparison to forensic samples

57
Q

certified reference material

A

material for which values are obtained by a technically valid procedure and accompanied by, or traceable to, a certificate or other documentation which is issued by a certifying body (e.g., NIST)

58
Q

CODIS

A

Combined DNA Index System administered by the FBI
CODIS links DNA evidence obtained from crime scenes, thereby identifying serial criminals
compares crime scene evidence to DNA profiles from offenders, thereby providing
investigators with the identity of the putative perpetrator
contains profiles from missing persons, unidentified human remains, and relatives of missing persons
there are three levels of CODIS: the Local DNA Index System (LDIS), used by
individual laboratories; the State DNA Index System (SDIS), used at the state level to serve as a state’s DNA database containing DNA profiles from LDIS laboratories; and the National DNA Index System (NDIS), managed by the FBI as the nation’s DNA database containing all DNA profiles uploaded by participating states

59
Q

CODIS user

A

an employee or contract employee who has login access to the CODIS (i.e.,
State or Local) system and is authorized to read, add, modify and/or delete DNA records in CODIS

60
Q

competency testing

A

a test or series of tests (practical, written, and/or oral) designed to establish that an individual has demonstrated achievement of technical skills and met minimum standards of knowledge necessary to perform forensic DNA analysis

61
Q

competency

A

the demonstration of technical skills and knowledge necessary to perform forensic DNA analysis successfully

62
Q

contamination

A

the unintentional introduction of exogenous DNA into a sample or analytical control during DNA testing

63
Q

continuing education

A

an educational activity (such as a class, lecture series, conference,
seminar, or short course) that is offered by a recognized organization or individual that brings participants up-to-date in their relevant area of knowledge

64
Q

corrective action plan

A

evaluates and remediates a nonconformity with the goal to identify, correct, and/or prevent reoccurrence of the nonconformity, when possible

65
Q

critical equipment/instruments

A

those equipment/instruments whose accurate functionality directly affects the results of the analysis and requires calibration, certification, or performance check prior to use and periodically thereafter

66
Q

critical reagents

A

those whose performance is vital to the success of the DNA testing and require testing on known samples before use on forensic or casework reference samples

67
Q

disposition of evidence

A

the documentation of the retention, return, or consumption of the evidence item(s) upon completion of DNA testing

68
Q

DNA record

A
69
Q

electrophoresis detection system

A

a platform that allows for the size separation of DNA molecules through a fluid or a gel under the influence of an electric field and the subsequent detection of the separated molecules by fluorescence or other means

70
Q

evidence

A

an item submitted for DNA testing and/or a derivative of an item as defined by the laboratory that is subject to a chain of custody

71
Q

expert system

A

a software program or set of software programs designed to interpret single source DNA data in accordance with laboratory defined quality assurance rules and identify DNA data not satisfying laboratory defined quality assurance rules, without human intervention

72
Q

forensic DNA analysis

A

(also referred to as Forensic DNA testing) is the process of isolation, detection, identification, and evaluation of biological evidence in criminal matters using DNA technologies

73
Q

forensic sample

A

a biological sample originating from and associated with evidence from a crime scene
a sample associated with evidence from a crime scene may include a sample that has been carried away from the crime scene

74
Q

functional testing

A

a process to confirm that a software performs the tasks as expected

75
Q

genetics

A

the study of inherited traits, genotype/phenotype relationships, and population/species differences in allele and genotype frequencies

76
Q

guidelines

A

a set of general principles used to provide direction and parameters for decision making

77
Q

interpretation software

A

a tool to assist the analyst in assessing the analyzed data by applying quality assurance rules, performing mixture deconvolution, and/or evaluating comparisons
interpretation software may include probabilistic genotyping software or expert systems

78
Q

known samples

A

biological material whose identity or DNA type is established

79
Q

laboratory

A

a facility:
1. employing at least two full-time employees who are qualified analysts
2. having and maintaining the capability to perform the DNA analysis of forensic samples and/or casework reference samples at that facility

80
Q

laboratory support personnel

A

employees or contract employees who perform laboratory support duties exclusive of analytical procedures on forensic or casework reference samples

81
Q

module

A

an independent but interrelated part of software that performs a distinct function

82
Q

molecular biology

A

the study of the theories, methods, and techniques used in the study and analysis of gene structure, organization, and function

83
Q

negative amplification control

A

an analytical control that is used to detect DNA contamination of the amplification reagents
this analytical control consists of only amplification reagents without the intentional addition of template DNA

84
Q

NIST

A

National Institute of Standards and Technology

85
Q

nonconformity

A

not meeting, implementing, maintaining, or complying with one or more of the requirements of these standards or a laboratory’s procedures, policies, or other quality system documents

86
Q

outsourcing

A

the utilization of a vendor laboratory to provide DNA services in which the NDIS participating laboratory takes or retains ownership of the DNA data
outsourcing does not require the existence of a contractual agreement or the exchange of funds

87
Q

performance check

A

a quality assurance measure to assess the functionality of laboratory critical equipment and instruments

88
Q

policy

A

an organization’s high level plan for a course of action or to address a requirement

89
Q

polymerase chain reaction (PCR)

A

an enzymatic process by which a specific region of DNA is replicated during repetitive cycles, which consist of the following:
1. denaturation of the template
2. annealing of primers to complementary sequences at an empirically determined temperature
3. extension of the bound primers by a DNA polymerase

90
Q

positive amplification control

A

an analytical control that is used to determine if the PCR performed properly
this control consists of the amplification reagents and a known DNA sample

91
Q

precision

A

characterizes the degree of mutual agreement among a series of individual measurements, values, and/or results

92
Q

preferential amplification

A

the unequal amplification of the two alleles present in a heterozygous locus during the polymerase chain reaction

93
Q

procedure

A

(protocol, standard operating procedure, or other equivalent) is a series of instructions to be followed in performing a specified task or under specific circumstances

94
Q

proficiency testing

A

a quality assurance measure used to monitor performance and identify areas in which improvement may be needed
proficiency tests may be classified as:
1. an internal proficiency test, which is produced by the agency undergoing the
test
2. an external proficiency test, which is a test obtained from a proficiency test provider accredited to the current applicable standard of the International Organization for Standardization and the applicable test is included on the proficiency test provider’s scope of accreditation

95
Q

qualified

A

an adjective used to describe an individual who meets the requirements for the position, has successfully completed the laboratory’s applicable training requirements, and is authorized to perform a specific task or role

96
Q

quantitative PCR (qPCR)

A

RT PCR - a method of determining the concentration of DNA in a sample by use of the polymerase chain reaction

97
Q

reagent

A

a substance or mixture of substances used in the analysis process to detect, measure, produce, or interact with other substances

98
Q

reagent blank control

A

an analytical control that is used to monitor contamination from extraction to DNA typing results and contains no intentionally added template DNA

99
Q

review

A

an evaluation of documentation to check for consistency, accuracy, completeness, and compliance

100
Q

semi-annual

A

used to describe an event that takes place two times during one calendar
year, with the first event taking place in the first six months of that year and the second event taking place in the second six months of that year, and where the interval between the two events is at least four months and not more than eight months

101
Q

sensitivity studies

A

are used to assess the ability to obtain reliable results from a range of DNA quantities, to include the upper and lower limits of the assay
also used to assess the ability of the system to reliably determine the presence of a contributor’s DNA over a broad variety of evidentiary typing results (to include mixtures and low-level DNA quantities)

102
Q

specificity studies

A

used to evaluate the ability of the system to provide reliable results over a broad variety of evidentiary typing results (to include mixtures and low-level DNA quantities)

103
Q

stochastic threshold

A

the peak height or signal magnitude value, determined through validation studies, below which it is reasonable to assume that, at a given locus, allelic dropout of a sister allele in a heterozygous pair may have occurred

104
Q

technical leader

A

an employee who is accountable for the technical operations of the laboratory and who is authorized to initiate, suspend, and resume laboratory operations

105
Q

technical review

A

an evaluation of reports, notes, data, and other documents to ensure there is an appropriate and sufficient basis for the scientific conclusions

106
Q

technical reviewer

A

an employee or contract employee who is a current or previously qualified analyst that performs a technical review of, and is not an author of, the applicable report or its contents

107
Q

technician

A

an employee or contract employee who performs analytical procedures on forensic samples or casework reference samples under the direction of a qualified analyst
technicians do not interpret data to reach conclusions on typing results or prepare final reports

108
Q

test kit

A

a preassembled set of reagents (or laboratory assembled equivalent) that allows the user to conduct a specific DNA extraction, quantification, or amplification method
a laboratory assembled equivalent may be referred to as a test system

109
Q

typing test kit

A

a preassembled set of reagents (or laboratory assembled equivalent) that is used to generate a DNA type

110
Q

uninterpretable

A

a determination that DNA data cannot be interpreted (e.g., due to poor or limited data quality, data that fail to meet laboratory quality requirements)
uninterpretable data may result in an inconclusive conclusion

111
Q

validation

A

a process by which a method is evaluated to determine its efficacy and reliability for forensic casework analysis and includes the following:
1. developmental validation, which is the acquisition of test data and determination of conditions and limitations of a new or novel DNA method for use on forensic samples
2. internal validation, which is an accumulation of test data within the laboratory to demonstrate that established methods and procedures perform as expected in the laboratory

112
Q

work product

A

the material that is generated as a function of analysis that is not subject to a chain of custody

analyst training (4 decks)

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