LECTURE 6: CSI QA & QC // CHAPTER 13 NATURE OF EVIDENCE

Question 1

Quality Control (QC)

Answer 1

• Monitoring processes with the aim of detecting nonconforming product.
• Involves measuring, testing, and inspection
• It is a reactive process. Doyle (2018)
• Ie tasting a sausage on a BBQ to see if its cooked

Question 2

Quality Assurance (QA)

Answer 2

• Aimed at prevention of nonconformance
• Achieved through planning
• Proactive process
• Undertaking tests in ADVANCE, so we know how long the sausage requires at
• what temp

Question 3

ISO

Answer 3

• International Organization for Standardization

Question 4

ISO/IEC 17025 and 17020

Answer 4

• Requirements for forensic science providers to demonstrate that they operate competently, and results can be relied upon

Question 5

Validation

Answer 5

• Confirmation by examination and provision of objective evidence that the particular requirements for a specific intended use are fulfilled
• Method Validation - The process of establishing the performance characteristics and limitations of a method and the identification of the influences which may change these characteristics and to what extent. Which analytes can it determine in which matrices in the presence of which interferences? Within these conditions what levels of precision and accuracy can be achieved? The process for verifying that a method is fit for purpose; i.e. for use of solving a particular analytical problem (Eurachem, 1998).

Question 6

Verification

Answer 6

• Confirmation by examination and provision of objective evidence that specified requirements have been fulfilled
• Verification is the process of demonstrating the performance criteria included in the method can be met by the facility prior to introducing them for routine use.

Question 7

Validation of a New Test

Answer 7

• Range in which the calibration equation applies (linearity of calibration)
  o Ie standards ranging between 0 and 10ng/uL
• Matrix Effects
  o Does the result differ depending on how the sample is collected
   DNA on a swab compared to a tapelift
   DNA derived from blood vs that from touch
• Selectivity
  o Is it measuring ONLY what its supposed to measure
   Can contaminants result in a false positive or negative
• Accuracy and precision
• Repeatability
  o Same result from single input across multiple instruments/operators
• Reproducibility
  o As per repeatability but across multiple input parameters
• Limit of Detection
  o Lowest possible result
• Measurement uncertainty
  o Result +/- error

Question 8

Sensitivity

Answer 8

o What is the minimum detectable amount
o Of all the actual positives, how many do we get right?
 Tendency for false negative

Question 9

Specificity

Answer 9

o Of all the actual negatives, how many do we get right
o Tendency for false positive
- Best assay is 100% sensitivity, 100% specificity

Question 10

What is evidence

Answer 10

• Whoever (judge/ jury) determines guilt or innocence is called the trier-of-fact
   Done through presentation of information of evidence
• Evidence defined: information - whether in the form of personal testimony, the language of documents, or the production of material objects - that is given in a legal investigation to make a fact or proposition more or less likely

Question 11

Circumstantial evidence

Answer 11

Evidence based on inference and not on personal knowledge or observation

Question 12

Conclusive evidence

Answer 12

evidence so strong as to overbear any other evidence to the contrary

Question 13

Conflicting evidence

Answer 13

Irreconcilable evidence that comes from different sources

Question 14

Corroborating evidence

Answer 14

Evidence that differs from but strengthens or confirms other evidence

Question 15

Derivative evidence

Answer 15

evidence that is discovered as a result of illegally obtained evidence and is therefore an invisible because of the primary taint

Question 16

Exculpatory evidence

Answer 16

evidence tending to establish a criminal defendants innocence

Question 17

Foundational evidence

Answer 17

evidence that determines the admissibility of other evidence

Question 18

Hearsay

Answer 18

testimony that is given by a witness who relates not what he or she knows personally but what others have said and that it is therefore dependent on the credibility of someone other than the witness

Question 19

Incriminating evidence

Answer 19

evidence tending to establish guilt or from which effect trier can infer guilt

Question 20

Presumptive evidence

Answer 20

evident deemed true and sufficient unless discredited by other evidence

Question 21

Prima facie evidence

Answer 21

evidence able establish a fact or sustain a judgement unless contradictory evidence is produced

Question 22

Probative evidence

Answer 22

evidence that tends to prove or disprove a point in issue

Question 23

Rebuttal evidence

Answer 23

evidence offered to disprove or contradict the evidence presented by opposing party

Question 24

Tainted evidence

Answer 24

evidence that is inadmissible because it was directly or indirectly obtained illegally

Question 25

Locard’s principle

Answer 25

• When two things interact – information is exchanged – two components to evidence considered this way: these are transfer and persistence.
  Locard’s principle does not imply that you probably won’t end up with fabric fibres on your clothes after sitting on a fabric couch.
  Consider a situation where you hug someone who is wearing a woolen jumper. If the hug lasts a long time, you would expect that more fibres are transferred than if the hug is short. If, instead of hugging, you touched their shoulder briefly, less fibres are transferred than the hug because the surface area of contact is smaller.
  Material that is transferred will persist until it further transfers, degrades or is collected as evidence. Consider the figure below showing the typical fibre loss curve for wool and complete the following statements:
  After one hour, approximately 35% of fibres will persist (that is, remain). After six hours, approximately 90% of fibres will have been lost.