Statistical Interpretation in Making DNA-based Identification of Mass Victims

Transcription

1 Statistical Interretation in Making DNAbased Identification of Mass Victims KyoungJin Shin wan Young Lee Woo Ick Yang Eunho a Det. of Forensic Medicine Yonsei University College of Medicine Det. of Information and Statistics Yonsei University DNAbased Identification of Mass Victims Direct Matching assesses the robability or likelihood that a DNA rofile from a victim s remains and a rofile develoed from a ersonal item known to belong to a missing individual would shareby chancethe same DNA rofile Indirect Matching uses methods of formal genetic kinshi htt://

2 Consideration for DNAbased Identification of Mass Victims Calculation of likelihood ratio LR Various kinshi Numerous families Allele droin and droout Estimation of cold hit Evaluation of DNA Analysis Odds Form of Bayes Theorem d E E E E d d osterior Odds Likelihood Ratio rior Odds

3 3 Kinshi robability LR LR 5 robability rior if ] [ + + E. LR LR E and two individuals of genotyes the be and. unrelated are and : etc. cousins full sibs child arent for examle related are and :. d LR d d d d d

4 Use of the IBD robabilities According to Balding and Nichols Forensic Sci Int.994;64 :5 4 Z Z Z : : : alleles allele alleles are identical by descent with is identical by descent with are identical by descent with robability robability robability Z + + Z Z The likelihood Ratio for the roosition That the Individuals and are Related Versus Unrelated d LR d aa ab aa ab bb or bc aa ab ac cc or cd + + a a 4 + a a b + + a 4a a b and ; the robabilities that and share or airs of autosomal STR alleles identicalbydecent 4

5 The robabilities and that a iven Relative and Me Share or airs of Autosomal STR Alleles Identicalbydescent Legend: reat reat randarent 7/8 /8 Relationshi reat randarent 3/4 /4 reat rand Uncle reat rand Aunt 7/8 /8 randarent / / rand Uncle rand Aunt 3/4 /4 First Cousin of randarent 5/6 /6 Mother Father Unrelated Uncle/Aunt / / First Cousin of arent 7/8 /8 Second Cousin of arent 3/3 /3 Me Full Sibling alf Sibling First Cousin Second Cousin Third Cousin /4 / /4 / / 3/4 /4 5/6 /6 63/64 /64 eneral Formula for LR Calculation According to Brenner and Weir Theor oul Biol. 3;63:73 8. a If two genotyes with susected relationshis are ab and cd define the four mating combinations : ac; : ad; 3: bc; 4 : bd. b If the two alleles in the ith air are the same tye then ui is the recirocal of the frequency of that allele. Otherwise ui. u + u + u 3 + u. a U 4 uu 4 + u u 3 b W 3. LR + U + W 4 5

6 Common IBD robabilities and LR Relationshi LR + U + W Not related LR Same individual LR W Discrimination index arentchild LR U aternity Index randarentgrandchild ½ ½ LR ½ + ½ U Full sibs ¼ ½ ¼ LR ¼ + ½ U + ¼ W alf sibs ½ ½ LR ½ + ½ U Unclenehew ½ ½ LR ½ + ½ U First cousin ¾ ¼ LR ¾ + ¼ U 6

7 Distribution of the LR Buckleton et al. Forensic DNA Evidence Interretation enotying of ighly Degraded DNA Efficient DNA extraction MiniSTR Identifiler + Minifiler ABI Yfiler + Yminilex ark et al 7 LR calculation should be modified in light of allele droout 7

8 The Likelihood Ratio LR for the roosition that the Individuals and are Related versus Unrelated d where a articular Allele in the rofile has Droed Out an an aa + LR d D + a + + D ad + Da ab D+ + D a + D + ad + Da bb or bc D + D + Da D ; the robability that a articular allele in rofile has droed out ; the robabilities that and share or air of autosomal STR alleles identicalbydescent LR equation from Buckleton et al. of which some notations are modified 8

9 Mitochondrial DNA Control Region Sequence of a Victim and the Alleged Brother Samle V V V3 alo grou Victim 63T636C 7394T63 39.C35.C 489C53d54d D4bb Brother 63T636C 7394T63 39.C35.C 489C53d54d D4bb Match robability /44 enotying of YSTRs using Yfiler kit from a Victim 9

10 enotying of YSTRs using Yminilex from a Victim YSTR enotyes of a Victim and the Alleged Brother STR locus DYS9 DYS389I DYS389II DYS39 DYS39 DYS39 DYS393 DYS385a/b DYS437 DYS438 DYS439 DYS448 DYS456 DYS458 DYS635 ATA 4. Allele Victim Brother Match robability /33 Shared Allele

11 enotying of Autosomal STRs using Identifiler kit from a Victim enotying of Autosomal STRs using Minifiler kit from a Victim

12 An Examle of Likelihood Ratio LR Calculation for Full Sibling with robabilities of Droout : D ¼ and ½ STR Locus Victim enotye Brother D LR Sibling Index D 4 D D8S DS D7S CSFO D3S T D3S D6S DS D9S vwa TOX 8 D8S D5S FA Cummulative LR The STR loci and alleles which have ossibility of allele droout and their LRs are reresented in bold italic. robability for Kinshi Determination N: No. of victims M: No. of genotyed skeletal remains n: No. of genotyed families M N M k n k X k N n 단 n k N M k n k M n N

13 Estimation of Cold it M E X n N For examle identification of Korean War victims Summary A simle and general formula for likelihood ratio calculation Evaluation of kinshi index in light of allele droout Estimation of cold hit in DNAbased identification on oen forms of mass disaster 3

14 Consideration for Use of LR LR threshold for determination of kinshi Rate of allele droout Degree of DNA degradation STR locus used in CR system Strategy to increase LR Use of mtdna YSTR halotyes Combined calculation of two more relatives genotyes Thank you for your attention! htt://forensic.yonsei.ac.kr 4