Forensic Investigative Genetic Genealogy Flashcards
1
Q
during the Pitchfork case, Jeffreys used a type of repeating (DNA) sequences, different to the ones used today. The repeated segments, in this case dozens or even 100 bases long can be observed. These are referred to as?
A
minisatellites
2
Q
What are minisatellites
A
- highly variable sequences (STRs)
- non-coding
- repeated within gene
- sometimes called variable number tandem repeats (VNTRs)
- range between 9 and 80 base pairs
- approximately 60 % of non-coding DNA consists of short sequences repeated over and over
3
Q
What is familial searchiing?
A
- uses the NDNAD to identify individuals who have genetic potential to be related to the individual who left the crime scene profile
- can be used to identify potential suspects who are not in the database
4
Q
What might cause no matches on database?
A
- person moved abroad
- Interpol searches
- person may be in prison/hospital (prisoner swabbing programme 2003)
- mental health act
- person may not have re-offended
- person re-offending in a category of crime not routinely sampled by a force (however unlikely given approach of most forces since 2006)
- crime may not have been reported
- person may have died
- person may have never been caught
5
Q
What other tools may be used if there is no match on the database?
A
- familial searches
- Y STR
- rare allele mapping
- intelligence led screens
- FIGG (forensic investigative genetic genealogy
6
Q
What have studies shown family dispersion is correlated with?
A
- higher income
- higher education
- criminality runs in families
- offenders operate close to where they live or in an area with which they are familiar
(location of relative may lead to suspect)
7
Q
What case showcased familial searching?
A
- murders of three teenage girls in 1973 in South Wales
- in 2000, NDNAD searched for profiles of possible relatives to murderer
- gave < 100 names after filtered for South Wales
- DNA samples volunteered from relatives
- in 2000 - called operation magnum
- Joseph Kappen exhumed in 2002
- tooth and femur sampled and DNA match obtained
8
Q
Richard third DNA tests
A
- latest genetic tests have uncovered evidence of another royal sex scandal. - the indiscretion could potentially undermine the legitimacy of the entire House of Plantagenet.
- skeleton of Richard III, the last Plantagenet King, was discovered under a car park in Leicester in 2012
- his identity was confirmed through his mitochondrial DNA, passed down through the maternal line from his sister to two relatives alive today
9
Q
How is familial searching done?
A
- look for 2 types of relative using 2 different computer programmes
- parents of children of offender
- siblings of the offender
10
Q
How are siblings used for familial searching?
A
- siblings have same parents
- they inherit 50 % of their DNA from each parent
- siblings are likely to share more DNA with each other than with unrelated individuals who have inherited their DNA from a different set of parents
11
Q
What two things are used in familial searching?
A
- Y-STRs for males
- mitochondrial DNA for females
12
Q
How are Y-STR’s used in familial searching and screening?
A
- if a male appears on the familial lists as a possible parent, child or sibling of the offender, in order for that to be true, his Y-STR must match that of the crime scene stain
- if it does not, all his male siblings, together with his biological father and all his sons are eliminated as possible offenders
13
Q
How is mitochondrial DNA used in familial searching?
A
- If a female appears on the familial search results lists as a possible parent or sibling of the offender, in order for that to be true, her Mitochondrial DNA profile must match that of the crime scene stain.
- if it is does not match, all her siblings and her children are eliminated as possible offenders but her father is NOT eliminated in this situation
14
Q
What are the results from familial searching?
A
- two different computer programmes search entire NDNAD
- each will product a list of candidate profiles:
- parent/child list (profiles have at least one matching DNA band at each of the 17 loci
- sibling list (a list with number of matching DNA bands)
- lists may contain 1000s of individuals so need to be prioritised (discuss with police)
15
Q
How are likelihood ratios used in familial searching?
A
- it is a number that represents how likely an individual is to be related to offender
- calculated based on which alleles (as well as how many) the individual shares with the offender and how rare these are in the general population
- higher number = more likely the person is to be related
- a likelihood ratio allows ranking of both parent child and sibling results
