Statistical Calculations in Case of Brother-Sister Incest

Nadia F. Salman, Hanan K. Mahmood, Sp.B Eman A. Hussain


Incest is a sexual activity that happens between close family members that are not allowed to get married due to customs or law. In a case of incest between a brother and his married sister, a paternity test and a
statistical analysis were performed at the laboratories of the Paternity and Kinship Division of the Medico-legal Directorate Baghdad, Iraq. Blood samples were taken from the concerned subjects in this case (newborn baby, mother, alleged father, and the husband) and placed on FTA cards. DNA extraction was done using Chelex®, then the
amplification of extracted DNA was carried out using an AmpFlSTR® Identifiler kit. PCR products were run with a 3130xl Genetic Analyzer, and the data were analyzed with Gene-Mapper ID® Analysis Software V.3.2 software.The analysis of DNA profiles using 15 loci as well as the statistical analysis for calculating the paternity index confirmed the allegation of the brother-sister incest, since the baby inherited all the obligate alleles from the alleged father (suspected brother). With a 99.9998% probability of paternity, these results showed that even in the case of brother-sister incest, paternity could be proved using 15 DNA locus with a high rate of certainty.


Forensic Science, Paternity, Incest, DNA Profile, Combined Paternity Index, Probability of Paternity.

Full Text:



Read DW. Incest taboos and kinship: a biological or a cultural story?. Reviews in Anthropology. 2014 Apr 3;43(2):150-75.

Tidefors I, Arvidsson H, Ingevaldson S, Larsson M. Sibling incest: A literature review and a clinical study. Journal of Sexual Aggression. 2010 Nov 1;16(3):347-60.

Courtois CA. Healing the incest wound: A treatment update with attention to recovered-memory issues. American Journal of Psychotherapy. 1997 Oct;51(4):464-96.

Turney L, Gilding M, Critchley C, Shields P, Bakacs L, Butler KA. DNA paternity testing: Public perceptions and the influence of gender. Australian Journal of Emerging Technologies and Society. 2003;1(1):21-37.

Ma H, Zhu H, Guan F, Cherng S. Paternity testing. Journal of American Science. 2006;2(4):76-92.

Draper H, Ives J. Paternity testing: a poor test of fatherhood. Journal of Social Welfare and Family Law. 2009 Dec 1;31(4):407-18.

Goodwin W, Linacre A, Hadi S. An introduction to forensic genetics. John Wiley & Sons; 2007.

Butler JM. Forensic DNA typing: biology, technology, and genetics of STR markers. Elsevier; 2005 Feb

Thomson JA, Pilotti V, Stevens P, Ayres KL, Debenham PG. Validation of short tandem repeat analysis for the investigation of cases of disputed paternity. Forensic science international. 1999 Mar 15;100(1-2):1-6. 10. Weir EI. Interpreting DNA evidence: statistical genetics for forensic scientists. Sinauer Associates Sunderland MA; 1998.

Schanfield M. DNA parentage testing (2003). Siegel JA, Saukko PJ, Knupfer GC, editors. Encyclopedia

of Forensic Sciences, Volumes 1-3. Academic Press; 2000.

Gjertson DW, Brenner CH, Baur MP, Carracedo A, Guidet F, Luque JA, Lessig R, Mayr WR, Pascali VL,

Prinz M, Schneider PM. ISFG: recommendations on biostatistics in paternity testing. Forensic Science International: Genetics. 2007 Dec 1;1(3-4):223-31.

Tamura A, Tsuji H, Miyazaki T, Iwata M, Nishio H, Hashimoto T, Kamiyama K, Suzuki K. Sibling incest

and formulation of paternity probability: case report. Legal medicine. 2000 Dec 1;2(4):189-96.

Macan M, Uvodic P, Botica V. Paternity testing in case of brother-sister incest. Croatian medical journal. 2003 Jun 1;44(3):347-9.

Canturk KM, Emre R, Gurkan C, Komur I, Muslumanoglu O, Dogan M. An incest case with three biological brothers as alleged fathers: Even 22 autosomal STR loci analysis would not suffice without the mother. Medicine, Science and the Law. 2016 Jul;56(3):210-2.



  • There are currently no refbacks.

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.