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DNA Statistics



The weight of a DNA profile match is determined using statistical methodology. There are several reputable individuals who have tackled this area of forensic science. STR analysis has allowed better resolution of DNA mixtures and the statistical theory has kept pace. This page presents legal decisions concerning the statistics of DNA profile matches and DNA mixture calculations.

  1. Michigan v. Laurence Deane Coy I1 (DNA Mixture calculation) mivscoy.PDF
  2. Arizona v. Garcia, 197 Ariz. 79, 3 P.3d 999 (Ariz. App. Div. 1, 1999)(DNA Mixture calculations admissible under Frye) garcia.PDF
  3. State v. Belken, 633 N.W.2d 786 (Iowa, Sep 06, 2001) (NO. 99-2001) belken.PDF
  4. Hills v. Com., 33 Va.App. 442, 534 S.E.2d 337 (Va.App., Sep 26, 2000) (NO. 0367-99-4) hill.DOC
  5. People v. Funston, (Cal.App. 3 Dist., Feb 28, 2002) (NO. C032472)(error-rate statistics not allowed). funston.PDF
  6. Butler v. State, 2002 WL 926283 (Fla., 5/9/02) (NO. SC95158). butler.PDF
  7. Darling v. State, 808 So.2d 145, 27 Fla. L. Weekly S41 (Fla., 1/3/02) (NO. SC94691). darling.PDF
  8. Minnesota v. Thoms, Minnesota Court of Appeals, 7/2/02, 2002 WL 142074 (expressing a percentage exclusion statistic rather than a random match statistic was proper). thomsAP.PDF
  9. R. v. Keir, NSWSC (New South Wales Supreme Court - Court of Criminal Appeal)(the significance of the statistical evidence was improperly stated to the jury). keir.PDF
  10. Dayton v. State, 2002 WL 1352496, Alaska App.,2002 (challenge to the database & admissibility of a genetic profile frequency) . dayton.PDF
  11. R v. Karger (Supreme Court of South Australia - Court of Criminal Appeal 8/30/02)(discussion of the use of the likelihood ratio and match probability). R. v. karger.PDF
  12. Com. v. Jones, 2002 WL 31630346 Pa.Super., 11/22/02 (failing to object to an expert's testimony that the defendant was the source of the DNA at the crime scene was not ineffective assistance of counsel). Jones.PDF
  13. Montana v. Ayers, 68 P.3d 768, 2003 (DNA mixture calculation using the likelihood ratio was admissible). Ayers.PDF
  14. Young v. Maryland, Court of Appeals, No. 99, 7/19/05, (An attribution statement of ID was proper without the statistics). Young.PD
  15. US v. Jenkins, District of Columbia Court of Appeals, No 05-CO-33,12/15/05 (a rarity statistic alone was admissible even where there was a database hit). US v Jenkins.PDF
  16. People v. Brownlow, District Court, Adams County, Colorado 5/18/06, the statistical probability of the match of the defendant's DNA and the DNA found at the crime scene was admissible even though the match was discovered through a CODIS "cold hit". Brownlow.PDF
  17. California v. Johnson, Cal. CA 5th District #F046939, 5/25/06, (No new methodology is involved when there is a CODIS database hit and scientifically-accepted techniques are used to determine the statistical significance of the match in the general population. Michael Johnson.pdf
  18. People v. Wilson, California Supreme Court, #S130157, 7/6/06 (there is no reason to preclude testimony of a range of ethnic or racial genetic profile frequencies when the race of the perpetrator is unknown, so long as the data is not presented in a manner that assumes that the race of the perpetrator is the same as the race of the defendant). Wilson.PDF
  19. People v. Nelson, California, CA 3rd District(Sacramento)#C047366, 8/31/06, the scientific community has generally accepted the random match probability derived through the product rule in a DNA CODIS databank hit. Nelson.PDF Affirmed in by the California Supreme Court in People v. Nelson, S147051, 6/16/08. Nelson SCt.PDF
  20. Roberts v. US, District Of Columbia Court of Appeals, No. 03-CF-853, 2/15/07 (any disagreement about the general reliability of interpreting mixed DNA samples is not an issue of admissibility, rather than one on which the defendant is free to cross-examine or present contrary expert testimony to the jury). Roberts v. US.PDF
  21. Minnesota v. Johnson, Hennepin County, Fourth Judicial District, No's: 02096915 and 04031951, 8/04, the defendants argued that the product rule should not be applied when a suspect is identified from a database search and the court denied their request for a Frye hearing on this issue. Johnson.PDF
  22. Minnesota v. Jackson, Hennepin County, Fourth Judicial District, No: 04085182, 1/06, the defendant argued that there should be a different rule for reporting the statistical frequency of a DNA profile if the suspect is identified by a database search. The court ruled that use the “product rule” was appropriate. Jackson.PDF
  23. Minnesota v. Blevins et al, Hennepin County, Fourth Judicial District, No's: 06020565, 05045926, 05073277, 06025878 and 05043793, 8/4/07, the scientific community has generally accepted the random match probability derived through the product rule in a DNA databank case and the defendants may through cross examination or through expert testimony question statistical probability calculations. Blevins.PDF
  24. Brown v. Farwell, U.S. Court of Appeals, Ninth Circuit, No. 06-30110, No. 07-15592, 5/5/08, the prosecutor erred when he presented statistical evidence to suggest that the DNA evidence indicates the likelihood of the defendant’s guilt rather than the odds of the evidence having been found in a randomly selected sample. Brown.PDF
  25. Minnesota v. Bartylla, Minnesota Supreme Court, No: A07-1166, 8/21/08, the court found that the expression of the statistical significance of a match between DNA samples raises questions of relevance but not of science, and no admissibility hearing is required to determine the admissibility of such evidence. Bartylla.PDF
  26. People v. Rojas, Colorado Court of Appeals, Div. VI, No. 05CA2058. 3- 6-08, the court upheld the admission of DNA mixture evidence and of testimony regarding the statistical probability that the DNA was that of a specific individual. Rojas.PDF
  27. State v. Dwyer, Maine Supreme Judicial Court, 2009 ME 127, Docket: And-08-709, 12/22/09, the trial court did not abuse its discretion by denying defendant’s motion seeking an order to require the state to perform a comparative search (an “Arizona search”) of its CODIS system to see if any of the database’s approximately 9000 records matched each other at nine or more loci. Dwyer.pdf
  28. Commonwealth v. Mattei, 920 N.E.2d 845, 455 Mass. 840, SJC-10390, Supreme Judicial Court of Massachusetts, Essex., 2/1/10, nonexclusion DNA results should not have been admitted without accompanying statistical explanation of the meaning of nonexclusion. Mattei.pdf