International Journal of Legal Medicine

, Volume 117, Issue 5, pp 302–305

Significance of micro-geographical population structure in forensic cases: a bayesian exploration

  • María T. Zarrabeitia
  • José A. Riancho
  • María V. Lareu
  • Francisco Leyva-Cobián
  • Angel Carracedo
Short Communication


We studied the influence of population structure at the microgeographical level on the analysis of forensic cases. A total of nine autosomal STRs and seven Y-STRs were analyzed in the general mixed population and in two relatively isolated valleys of Cantabria, a region in Northern Spain. Statistically significant differences existed in the frequency distribution of four autosomal STRs, with an overall Fst value of 0.3%. A simulation of virtual trio cases revealed that it did not have a practical influence on the analysis of paternity disputes. Significant differences also existed in most Y-STRs, with an overall Fst value of 3%. Thus, using the general database instead of the specific valley database resulted in 5-fold or higher overestimation of the likelihood ratio of matching in up to 30% of cases. A bayesian analysis revealed that this had a significant impact on the estimation of the probability of identity in scenarios of low "a priori" odds of suspicion.


Microsatellites STR Y-chromosome Evidence interpretation Population structure 


  1. 1.
    Budowle B, Shea B, Niezgoda S, Chakraborty R (2001) CODIS STR loci from 41 sample populations. J Forensic Sci 46:453–489PubMedGoogle Scholar
  2. 2.
    Zarrabeitia MT, Riancho JA, Leyva-Cobian F, Sanchez-Diz P, Carracedo A (2002) Differences in Y-chromosome haplotype frequencies at the microgeographical level. In: Brinkmann B, Carracedo A (eds) Progress in forensic genetics 9. Elsevier, Amsterdam, pp 409–412Google Scholar
  3. 3.
    Freeman S (1979) The Pasiegos. Chicago University Press, ChicagoGoogle Scholar
  4. 4.
    Moure A, Suárez M (eds) (1995) De la Montaña a Cantabria. La construcción de una comunidad autónoma. Publicaciones de la Universidad de Cantabria, SantanderGoogle Scholar
  5. 5.
    Gusmao L, Gonzalez-Neira A, Pestoni C, Brion M, Lareu MV, Carracedo A (1999) Robustness of the Y STRs DYS19, DYS389 I and II, DYS390 and DYS393: optimization of a PCR pentaplex. Forensic Sci Int 106:163–172PubMedGoogle Scholar
  6. 6.
    Gusmao L, Gonzalez-Neira A, Sanchez-Diz P, Lareu MV, Amorim A, Carracedo A (2000) Alternative primers for DYS391 typing: advantages of their application to forensic genetics. Forensic Sci Int 112:49–57PubMedGoogle Scholar
  7. 7.
    Kayser M, Caglia A, Corach D et al. (1997) Evaluation of Y-chromosomal STRs: a multicenter study. Int J Legal Med 110:125–133PubMedGoogle Scholar
  8. 8.
    Gill P, Brenner C, Brinkmann B et al. (2001) DNA Commission of the International Society of Forensic Genetics: recommendations on forensic analysis using Y-chromosome STRs. Int J Legal Med 114:305–309PubMedGoogle Scholar
  9. 9.
    Riancho JA, Zarrabeitia MT (2003) A windows-based software for common paternity and sibling analyses. Forensic Sci Int (in press)Google Scholar
  10. 10.
    Zarrabeitia MT, Riancho JA (2001) Population data on nine STRs from Cantabria, a mountainous region in northern Spain. Forensic Sci Int 122:175–177CrossRefPubMedGoogle Scholar
  11. 11.
    Riancho JA, Zarrabeitia MT (2002) The prosecutor's and the defendant's bayesian nomograms. Int J Legal Med 116:312–313PubMedGoogle Scholar
  12. 12.
    Tully G, Bar W, Brinkmann B, Carracedo A, Gill P, Morling N, Parson W, Schneider P (2001) Considerations by the European DNA profiling (EDNAP) group on the working practices, nomenclature and interpretation of mitochondrial DNA profiles. Forensic Sci Int 124:83–91CrossRefPubMedGoogle Scholar
  13. 13.
    Beleza S, Alves C, González-Neira A, Lareu M, Amorim A, Carracedo A, Gusmao L (2003) Extending STR markers in Y chromosome haplotypes. Int J Legal Med 117:27–33Google Scholar
  14. 14.
    Roewer L, Krawczak M, Willuweit S et al. (2001) Online reference database of European Y-chromosomal short tandem repeat (STR) haplotypes. Forensic Sci Int 118:106–113PubMedGoogle Scholar
  15. 15.
    Balding DJ, Nichols RA (1994) DNA profile match probability calculation: how to allow for population stratification, relatedness, database selection and single bands. Forensic Sci Int 64:125–140PubMedGoogle Scholar

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • María T. Zarrabeitia
    • 1
  • José A. Riancho
    • 2
  • María V. Lareu
    • 3
  • Francisco Leyva-Cobián
    • 2
  • Angel Carracedo
    • 3
  1. 1.Unit of Legal Medicine, Faculty of MedicineUniversity of CantabriaSantander Spain
  2. 2.Hospital Marqués de ValdecillaUniversity of CantabriaSantanderSpain
  3. 3.Institute of Legal MedicineUniversity of Santiago de CompostelaSantiago de CompostelaSpain

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