Presentation on theme: "3 Person Example #2 Suspect Boxer Shorts (The Ladies Man)"— Presentation transcript:
3 Person Example #2 Suspect Boxer Shorts (The Ladies Man)
The Scenario Victim accused Subject of rape in store room at a club But she waited 4 days to report it She could, however, describe the Thomas the Tank Engine boxers of her assailant Investigation led to Suspect who indeed had Thomas the Tank Engine boxers
The Scenario Accused said he didnt do it He said he couldnt have done it because he had sex with a waitress in the store room of the club that night The waitress said she had sex with him in the store room at the club
Enter question text... 1.Not interpretable by our guidelines 2.Mixture of 3 people – no stat 3.At least 3 people – no stat 4.Indeterminate mixture, CPI 5.We would exclude only 6.We have a way to deal with it including a stat
My Interpretation (This is the part you REALLY must do before looking at any references) Mixture Consistent with 3 persons 5 loci with nothing in the Danger Zone The remaining loci might have drop out Profile is interpretable and I can do a stat
The Interpretation Since you have 5 loci with everything above stutter, why not just do a 5 locus CPI? 4.6.3. When using CPE/CPI (with no assumptions of number of contributors) to calculate the probability that a randomly selected person would be excluded/included as a contributor to the mixture, loci with alleles below the stochastic threshold may not be used for statistical purposes to support an inclusion. In these instances, the potential for allelic dropout raises the possibility of contributors having genotypes not encompassed by the interpreted alleles. 18.104.22.168. Alleles below the stochastic threshold may be used for comparisons and/or to establish the presence of a mixture or male DNA (e.g., Y allele at amelogenin). 22.214.171.124. A restricted CPE/CPI may be applied to multiple major contributors despite the presence of minor contributor(s) alleles below the stochastic threshold; a description of how to calculate can be found in Section 5.3.5.
The Interpretation – CPI Cool! This one is easy D8 D7 D16 D13 THO1
The Interpretation – CPI 126.96.36.199. A restricted CPE/CPI may be applied So if I have a clear major(s) I can also use those loci! Maybe you could pull out a major here D18 D21 D19
The Interpretation – CPI But…. Unfortunately all those tall peaks match the owner of the boxers – (I peeked – we were going to interpret without looking at the references) – (If we hadnt at least looked at the assumed/expected person/owner, wed be in a mess) But we still have those 5 loci >300
The Interpretation – CPI But do we really have 5 loci >300 for all alleles? SWGDAM - loci with alleles below the stochastic threshold may not be used for statistical purposes But theres a huge hole in that
The Interpretation – CPI Look at THO1 Are we positive the 9 is from a single contributor? If not, its pretty much a given that: – Someone is contributing <300 – Therefore, we have allele(s) <300 – Therefore, we cant use that locus THO1
The Interpretation – CPI Look at D13 Pretty much certain that if we correct for stutter, 13 <300 So much for that locus Now were down to 3 loci for CPI D13
D8 and D7 are no better Are you 100% certain all contributors are >300? If there are 2 contributors to the 14 (D8) and the 8 (D7) someone MUST be <300 because both are <600 rfu (Plus the 8 is in stutter position) D7 The Interpretation – CPI D8
The Interpretation – CPI That leaves us with only D16 to consider There are only 2 alleles, and we already gave up on other loci like this for 2 person mixtures And its even worse than it seems - D16
The Interpretation – CPI D16 has ghost peaks So we know there are alleles missing here even though all detected alleles are >300 Bye, bye CPI
The Interpretation – Now what? RMP to the rescue! (With one problem at D16) But lets look down in the baseline before we decide how to move on
The Interpretation – mod RMP Other than D16 I have no other concerns about the baseline By that I mean I dont see anything that if it were real would change the interpretation of consistent with 3 contributors Lets look at some spots were it could possibly be argued thats not true, but I think it is
D3 5 Alleles called 3 more blips 5 + 3 = 8 so 4 people? The Interpretation – mod RMP 13 80 15.2 73 10 48
The Interpretation – mod RMP The 10 and 13 might be only stutter The 15.2 probably not Which would mean 6 alleles, so still 3 people 13 80 15.2 73 10 48
The Interpretation – mod RMP Worst case scenario – 4 people for D3? Correct for stutter (50%) 2 alleles go away Consistent with 3 people!
The Interpretation – mod RMP So at D3, what happens if I have a reference to compare that has a 15.2? As long as that persons other allele is found in the mixture there, they are still included Remember, Im allowing for Anys so I expect drop out is possible I wouldnt exclude, but would make locus = 1 for that person
The Interpretation – mod RMP D2 is similar Could there be an 18, 20 or 26? 2 of those are in stutter positions We can test it again – Do we have more than 6 alleles?
The Interpretation – mod RMP Worst case scenario – 4 people for D2? Correct for stutter (50%) 2 alleles <20 rfu Consistent with 3 people?
The Interpretation – mod RMP Do I need to worry about alleles below 20? NO WAY!! So, consistent with 3 people
The Interpretation – mod RMP So that was a really LOOOOONNNNNG discussion to say this: Just do a modified RMP – It covers for all the potential drop out here, since any drop out would still be consistent with 3 people – But, we have to drop D16 from the calculation – We KNOW there is drop out there
The Interpretation – mod RMP The actual stat takes about 3 clicks 1. Open the sample into the Mix Interp Window 2. Operations>Mixture Frequency 3. 3 contributors 4. Open Frequency Report (OK, 4 clicks)
D18 The Interpretation – mod RMP Quick look at D18 There are 3 Allele, Anys here
The Interpretation – mod RMP Quick look at D5 There is 1 Allele, Any here
The Interpretation – mod RMP Quick look at FGA 6 Alleles and 3 People, so subtract homozygotes
The Interpretation – mod RMP The Final Stat 1 in 13,400 (1 in 462,000 if D16 kept)
Last Thought Remember D16? The ghost alleles? We dropped that locus for the stat – Made it 1.0 mathematically – Its now a neutral locus The right LR model would cause D16 to be supportive of Hd if POI were 12, 13 (the ghost alleles)
Last Thought But, what form of the LR? – Unrestrained combinatorial method? – F or Q method? – D method? – Semi-continuous model? – Continuous model? How many of us know what we mean when we say I need LR with drop out?
Last Thought We are working hard to understand those LR models We are moving towards a LR model that incorporates Q and D We want to include our phr and p information that we currently use for RMP This could then be considered a semi- continuous LR
Oops! We Forgot Is Victim included or excluded as a contributor to the three person mixed DNA profile recovered from the boxers of the Accused? She cannot be excluded What about the waitress????