CRIM 2040 (Forensic Analysis) Flashcards Quiz 1

Frye standard

method by which that evidence was obtained was generally accepted by experts in the particular field in which it belongs 

Daubert standard

trial judge to assess whether an expert witness’s scientific testimony is based on scientifically valid reasoning that which can properly be applied to the facts at issue

Daubert determining whether the methodology is valid are 

1. Whether the theory or technique in question can be and has been tested 

2. Whether it has been subjected to peer review and publication 

3. Its known of potential error rate 

4. The existence and maintenance of standards controlling its operation 

5. Whether it has attracted widespread acceptance within a relevant scientific community

FRE 702

A witness may testify if

1. The experts scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;

2. The testimony is based on sufficient facts or data 

3. The testimony is the product of reliable principles and methods 

4. The expert has reliably applied the principles and methods to the facts of the case

foundational validity

• for a forensic science method requires that it be shown, based on empirical studies, to be repeatable, reproducible and accurate 

Objective

can replace with algorithm

Subjective

key procedures involve human judgement 

validity as applied

the method has been reliably applied in practice 

repeatable

with known probability an examiner obtains the same result, when analyzing samples from the same sources 

reproducible

with known probability, different examiners obtain the same result when analyzing the same samples 

accurate

with known probabilities an examiner obtains correct results both (1) for samples from the same source (true positives) and (2) for samples from different sources (true negatives)

reliability

repeatability, reproducibility, and accuracy 

consistent

same results each time

repeatable

same evidence same person

reproducible

same evidence different person

accurate

how close is it to the truth?

trier of fact/fact finder

judge or jury

empricial studies

data based, not memory of guesses 

replicates

random vriation

representative samples

test the right population

adequate sample sizes

otherwise noise obscures signal

false positives and false negatives

not just one of these

probative value

test alternative hypothesis

black box study

needs to be an empirical study, ground truth, and evaluating the correctness of answers

False positive

identifies something when really it shouldn’t have been

False negative

fails to identify something when really it should have been

Type I error

wrongful conviction, false alarm, false positive

Type II error

false negative, let guilty free

NAS 2009 Report

concluded with no forensic method has been shown to have the capacity to demonstrate a connection between evidence and a specific source

PCAST 2016 Report

concluded the need for clarity about the scientific standards for the validity of methods and the need to evaluate specific methods to determine whether they have been established to be valid and reliable

dry labbing

coming up with results without doing all the tests

latent print

crime scene print

exemplar print

cleaned fingerprint (yellow before, red after)

FBI study

false positive rate is 1 in 206

contextual bias

anlayst’s outside knowledge interferes with results

reverse reasoning

marking minutiae in clean print then marking latent print from scene leads to overreliance on similarities

experimental

A procedure carried out to support or refute a hypothesis.

error rates

validity must produce false negative and false positives