Contamination, Screening, Lab Technique Flashcards
what is the amended report (AR) 3125
subsection of ISO 17025 that applies directly to forensic testing laboratories
what does ANAB stand for and what does it do
- ANAB = ANSI (American National Science Institute) National Accreditation Board
- accredits the LSPCL every four years
define analytical control
a sample used to demonstrate that a method works correctly and then ensures the data is valid
explain the combined DNA index system (CODIS)
- US national DNA database that is maintained by the Federal Bureau of Investigation (FBI)
- there are twenty CODIS core STR loci required for upload of DNA profiles into the national DNA database
what is direct contamination
transfer of DNA from source of contamination to evidentiary item or sample
what is indirect contamination
transfer of DNA from the source of contamination to the evidentiary item or sample through an intermediary
what is an internal audit, how often are they performed, and who performs them
- performed by LSPCL employees who are qualified auditors
- ISO/AR internal audit: every year; LSPCL audits only follow these standards
- auditors must pass a course and competency test- FBI QAS internal audit: auditors must be a qualified DNA analyst and pass the FBI auditor course
- must meet requirements of QAS appendix C
what is an internal validation
the accumulation of test data within the laboratory to demonstrate that established methods and procedures perform as expected
what does ISO/IEC stand for and what does it do
- the acronym for the joint technical committee of the Internal Organization for Standardization and the Internal Electrotechnical Commission
- ISO/IEC develops, maintains, and promotes standards covering multiple industries
- ISO 17025: standards for testing laboratories
what is a performance check
a quality assurance measure to assess the functionality of laboratory critical equipment and instruments
examples of personal protective equipment (PPE)
lab coat, mask, gloves, etc.
what are quality assurance standards (QAS)
standards set by the FBI that are specific to DNA testing laboratories
what does SWGDAM stand for and what does it do
- the acronym for the Scientific Working Group on DNA Analysis Methods
- SWGDAM provides recommendations to the FBI and the United States forensic DNA community on quality assurance standards, research, protocols, and methodologies
what is the abacard hematrace test
- presumptive test for blood
- indicates human/non-human source for blood
what is acid phosphatase and what is it used for
- presumptive test for seminal fluid
- AP is an enzyme secreted in higher amounts by the prostate gland than anywhere else
what does azoospermic mean
- absence of sperm in ejaculate
- result of vasectomy
what is bulk evidence
any physical items collected at the crime scene
what are consumed items
when the entirety of the original evidence is used for testing; there is no excess to retain or re-test
what is contamination
the unintentional introduction of exogenous DNA into a sample or control during DNA testing
what are cuttings
- taken when the evidence examined is porous and there is an expectation that the biological material intended for analysis can penetrate past the surface
- for evidence, 1cm^2 - 1.5cm^2 is removed
- for references, 0.5cm ^2 - 1cm^2 is removed
- prepped for extraction in flip-cap 1.5mL conical tubes
what is documentation
- notes of the examination contemporaneous
- includes submission numbers, exhibit numbers, item descriptions, observations, photographs, SP#s, reagent lot numbers, individuals involved, and chain of custody
what is evidence
- anything that is collected from the crime scene
- swabs, bulk (weapons, clothing, tools, consumables), sexual assault kits (clothing, bedding, towels, condoms, devices), miscellaneous (vehicles, bones, hairs)
what are extraction sample types
- sexual assault kit samples: intimate and trace samples are processed differently
- blood: lots of DNA
- trace/contact: skin cells
- hair: root only
* hair shaft required for mitochondrial DNA testing
what is the “forensic question”
- the probative nature of the evidence
- WHO is on the evidence
- HOW do we get to the WHO on the evidence
- WHAT does getting the WHO on the evidence mean
what is the high dose hook effect
- occurs with excess antigen which binds to the stationary antihuman antibody in the “T” area
- prevents the mobile antibody-antigen complex from binding
what is microscopy for spermatozoa
- confirmatory test for spermatozoa (no longer performed at LSPCL)
- the presence of semen in questioned specimens can be confirmed by the observation of spermatozoa
- utilizes christmas tree stain
what does oligospermic mean
- lower than normal sperm count
- > 15 million sperm per 1 mL semen
what is the phenolphthalein test
- presumptive test for blood
- tests presence of hemoglobin
what is the prostate specific antigen test (PSA)
- presumptive test for seminal fluid
- tests for P30; only found in semen
what is screening
the examination and sampling of evidence for DNA analysis or preservation
what is serology
the testing and identification of bodily fluids
what are sexual assault kits (SAK)
- swabs, trace evidence (suspect hairs, debris), and clothing collected by trained medical professionals (SANE nurses)
- intimate swabs are forwarded to differential extraction
- non-intimate swabs are presumptively tested (AP test)
what is a state police number (SP#)
- unique to every case processed at LSPCL
- ex: #####-24
what are swabs
- a stick or rod with a fiber or foam-like material end used to collect biological substances
- for evidence, 1/2 - 2 swabs are taken
- for references, 1/2 - 1 oral reference swab is taken
- prepped for extraction in flip-cap 1.5mL conical tubes
tips for large volume pipetting
- insert pipette at an angle into the tube for ejecting/inserting liquid
- insert pipette tip into existing liquid
example pipetting techniques
- work at room temperature
- use correct pipette tips
- use constant plunger pressure and speed
- pull pipette straight out of any liquid
- avoid handling the pipette tip
- set the pipette down between samples
- eject tip in to proper waste receptacle
tips for small volume pipetting
- insert pipette straight into the bottom of the tube
- insert pipette tip into existing liquid
