RSS Evaluative Reporting Flashcards
What type of report provides an assessment of the strengths to be attached to findings?
Evaluative
Synonymous with transposing the conditional - is this type of fallacy?
Prosecutors fallacy
What is probability?
is a measurment of that event will occur
* quantified as a number between 0 and 1
* zero indicates impossibility of the event occuring
* one indicates certainty
What are the rules of probability?
- when an event cannot occur the probability will be 0
- when an event is certain to occur the probability is 1
- the sum of the probabilies of all the outcomes in the sample is 1
- the probability that an even will not occur is equal to 1 - the probability that the event will occur
What are the two factors that are required to determine probability?
- E the event whose probability is being considered
- I the information available to the assessor when the probability of E is being considered
What are the two things that probability can be?
- Objective: a logical measure of chance where everyone would be expected to agree to the value of the relevant probability
- Subjective: measuring the strength of a persons belief in a particular proposition
What is the notation that shows the probability that the accused is guilty given the evidence?
p (G|E)
What is the notation for the probability that the accused is innocent given the evidence introduced?
p (I|E)
What is Bayes Theorem?
Posterior odds = likelihood ratio x prior odds
What is the posterior odds in terms of probabilities?
Pr(Hp|Evidence) / Pr(Hd|Evidence)
Case of Lucia De Berk
- example of prosecutors fallacy
- statistician said the odds were 342 million to 1 that it was a coincidence she had been duty when all incidents occurred
- some deaths she wasnt actually present for
- statistic was recaculated and she was acquitted
What are the two types of samples?
- recovered or questioned samples (unknown origin)
- control or reference sample of known origin
What is relative frequency?
Calculated against the items observed over a period of time or from all DNA profiles in a defined population
How are the figures in the likelihood ratio formed?
- extensive surverys, databases or experimention
- personal experiences and previous casework
What are the two probabilities or likelihoods?
- the likelihood of the evidence if the prosecutions proposition is true
- the likelihood of the evidence if the defence proposition is true
What does the relative value of the two likelihoods provide?
- a measure of the meaning
- probative value of evidence
- represented as the likelihood ratio
What are the alternative names for prior odds?
- background rates
- base rate
What case demonstrates base rate level?
Benn and Benn
* base rate levels of drugs on banknotes
What is base rate fallacy?
making a probability judgement based on conditional probabilities without taking into account the effect of prior odds
The probability of guilt given the evidence and vice versa is an example of what odds?
Posterior
Frequencies can be both relative and?
Absolute
A logical measure of chance is referred to as this type of probability?
objective
What are three ways statistics can be expressed as?
- percentage
- proportion (relative frequency)
- probability/likelihood
Case of Reed and Reed (2009)
- shows issue around transfer
- plastic from two separate knife handles were found next the victims body
- cellular material on both pieces of plastic matched Reed and Reed
Give examples of where DNA samples can originate?
- bone
- hair
- vomit
- faeces
- skin flakes
- biological fluid
What three biological fluids are not detectable by visual examination or presumptive tests?
- sweat
- skin cells
- vaginal secretions
What was directed towards challenging the admissibility of evidence given by Valerie Tomlinson in the case of Reed and Reed?
the manner and timing of the transfer of the appelants DNA
Valerie Tomlinson issues
- her opinion was that the DNA transferred through primary transfer
- failed to account for the fact only a fragment of each handle was found
- did not consider the possibility that there might have been cellular material from others on the rest of the handle or blade
What issues was said about professor jamieson in the Reed & Reed?
- private commercial organisation
- not accredited by UKAS or any other body in England, Wales or Scotland
- experience in interpretating DNA profiles is limited
- doesnt conduct lab research
- not qualified to make a scene of crime investigation
Issues with source level propositions
- do not say anything about how evidence came to be at the scene
- dont take into account variables such as quantity, position or distribution
- can only address whether or not evidence came from a particular source
- require little in the way of circumstantial information
What is the ultimate issue which the court must deal with?
Offence level statements make conclusions about criminal responsibility and liability
Why should experts not testify to propositions at offence level?
- they involve factual and moral judgement that forensic scientists are not juridictionally competent to make
- was harm caused unlawfully
What words should be used for reporting the narrative?
- cannot be excluded
- consistent with
- could have come from
- could have originated from
What is relative frequency?
- empirical probability
- proportion of times that a particular event occurs relative to the total number of observations
If the relative frequency of the DNA in the general population is 1 in 1000, what is the probability that a suspect is guilty?
1- 1/1000 = 999/1000
Where the scientist can say that the source of DNA came from a particular body fluid. What terminal do we use here?
attributable
The non-DNA evidence, used in the case of Reed and Reed locating the offenders?
cell site analysis
What is the semantic scale that is sometimes used for the likelihood ratio?
- moderate support
- weak support
- strong support
- very strong support
What are the posterior odds equal to when they are in favour of the prosecution proposition?
the product of the ratio of the probability of the evidence if the prosecutions proposition is true, to the probability of the evidence, if the defence is true and the prior odds in favour of the prosecution proposition
