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United States v. Kootswatewa

United States District Court, D. Arizona

March 2, 2016

United States of America, Plaintiff,
Theodore Kootswatewa, Defendant.


Douglas L. Rayes United States District Judge

The Government alleges that Defendant Theodore Kootswatewa, a Hopi adult, sexually assaulted a Hopi girl inside an abandoned trailer owned by a Hopi woman on the Hopi reservation. (Doc. 1.) Pursuant to Federal Rules of Evidence 702 and 403, Defendant moves to preclude the Government’s expert from testifying about the probability of a random match of the Y-STR partial DNA profile identified on the victim. (Doc. 77.) The Court held an evidentiary hearing on Defendant’s motion on February 10, 2016. The Government and Defendant each presented one expert witness. The Court admitted five exhibits: two from the Government and three from Defendant. For the following reasons, the Court grants Defendant’s motion.


Deoxyribonucleic acid (“DNA”) is material found within cells throughout the human body that contains the information necessary to make a human being. (Doc. 100 at 10.) DNA analysis requires a four-step process. (Id. at 13.) Step one involves extraction of the DNA using chemicals to break open the cells. (Id.) Next, the quantity of the DNA obtained from the sample is determined in a process called “quantitation.” (Id.) Third, the examiner copies the relevant areas of the DNA using the “polymerase chain reaction” (“PCR”). (Id.) Finally, the DNA is separated by size to generate a DNA profile. (Id. at 13-14.) In criminal investigations, a DNA profile from cells found on a victim can be compared with samples from suspects to determine whether there is a match. (Id. at 14.) Because each person’s DNA is distinctive, the probability that a random person’s DNA profile would match the crime scene sample is extraordinarily low, sometimes one in several billion. (Id. at 10, 21-22.)

When a crime scene sample contains an excess amount of female DNA compared to male DNA, examiners employ a different process called “Y short tandem repeat” (“Y-STR”) DNA analysis. (Id. at 14.) The first two steps are the same as regular, autosomal DNA analysis. (Id. at 15.) From there, the process differs by utilizing a special kit that seeks out only the Y-chromosome, which is found only in males, instead of any of the other 22 pairs of chromosomes found in the human body. (Id. at 14-16.) The Y-chromosome DNA profile is then cross-referenced against a database of known samples to generate a statistical estimate of the probability that the profile would be observed randomly among certain populations. (Id. at 16-17.) This statistical calculation process is known as the “counting method.” (Id. at 21.)

A man’s Y-chromosome is inherited entirely from his biological father. (Id. at 22-23.) Identical Y-chromosomes are likely to be shared not only by immediate family members, such as fathers, sons, brothers and uncles, but also by very distant male relatives whose family relationship has centuries ago been lost. (Id.) Because there are fewer permutations when examining only the Y-chromosome than in the usual DNA examination, the extraordinarily low statistical probability of a random match of a full DNA profile does not exist with Y-STR analysis. (Id.) In other words, there are large numbers of other individuals who likely share any man’s Y-chromosome. For this reason, the results of Y-STR analysis only allow an examiner to determine whether a crime suspect and his male paternal relatives can be excluded as contributors.

Specific Y-STR profiles are not likely to be evenly dispersed among populations of the world. (Id. at 28-31.) Some populations have existed in relative isolation while others have been engaged in significant historical genetic mixing with other populations. For example, people living on a remote Pacific island in genetic isolation for thousands of years likely would not share Y-STR profiles with people living in Europe, but would share many Y-STR profiles with each other. Even though not geographically remote, some populations tend to mate preferentially with other members of the group and not with outsiders. The geographical remoteness and/or the preferential mating practices of certain populations have resulted in Y-STR clusters. Certain Y-STR profiles are common in some regions of the world or among certain ethnic groups but entirely absent among others. (Id.) Forensic scientists attempt to account for this non-random sorting by categorizing profile frequencies in terms of race. (Id. at 28, 30.) Probability statistics of a random Y-STR DNA match are expressed and qualified by the race of the individual for whom there is a match. For example, there are categories for Caucasians, African-Americans, and Native Americans. (Id.)

In this case, Erin Daniel, a criminalist with the Arizona Department of Public Safety crime lab in Flagstaff, examined external genital swabs from the victim, a swab from the crotch of her underwear, and buccal swabs from Defendant’s mouth. (Id. at 7, 19.) The DNA testing of the external genital swabs and the victim’s underwear revealed DNA of at least two individuals. (Id. at 20.) The major component of the DNA recovered was the victim’s own, which potentially blocked the ability to fully observe the other DNA. (Id.) Thus, Ms. Daniel examined the sample using Y-STR analysis. (Id.)

Ms. Daniel utilized the “YFiler” kit, manufactured by Applied Biosystems and made specifically for separating female DNA and copying the Y-chromosome. (Id. at 15-16.) She generated the DNA profile and found that it matched the profile of Defendant’s Y-chromosome on all 16 loci, meaning Defendant and his male paternal relatives could not be excluded as contributors. (Id. at 20.) Ms. Daniel then checked the profile against the Applied Biosystems database and determined that the profile has not been observed. (Id. at 20-21.) Based on the size of the Applied Biosystems database, Ms. Daniel concluded that the Y-STR profile from the crime scene sample is not expected to occur more frequently than in 1 in 35 Native Americans. (Id. at 21.)


The district court determines whether expert testimony is admissible. See Estate of Barabin v. AstenJohnson, Inc., 740 F.3d 457, 464-65 (9th Cir. 2014). Pursuant to Fed.R.Evid. 702:

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:
(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the ...

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