dissenting.
I respectfully dissent. I certainly agree that when Congress enacted section 1359, it intended to limit the statute’s application to persons whose ancestry is “50 per cen-tum of blood” of the American Indian race. So much is clear from the face of the statute. Understood literally, the statute would require anyone seeking to come within its protections to prove that at least half of his or her forebears were living on this continent before Columbus arrived. The majority opinion holds that section 1359 requires “some combination of evidence from which the finder of fact can reasonably conclude that the individual in fact possesses 50 per centum or more American Indian blood. Proof only that an individual possess some unidentifiable degree of Indian blood without more will be insufficient.” In this case, Curnew’s expert admitted that she could not reasonably state that Curnew possessed fifty percent American Indian blood. She was quite candid and fair in stating the obvious. The majority concludes that unless she could *1340state such an opinion within a reasonable degree of certainty as an expert, she would not be able to testify.
In reaching these conclusions, the majority has allowed the scientific ring of the term “50 per centum” to overwhelm a common sense meaning. The majority imposes an evidentiary requirement virtually prohibiting any individual from proving Indian ancestry under this provision, a result Congress could not have intended. The majority leaves entirely unclear the quantum of evidence it believes necessary for a jury to determine reasonably the proportion of the defendant’s Indian ancestry. This approach obscures the difficulty a defendant confronts in meeting the requirement imposed. The initial burden placed on a defendant to even identify the members of a family tree encompassing only three or four generations is prohibitively onerous.. However, under the majority’s literal reading of the statute, going back even four generations would likely not be sufficient since tracing ancestry that far would hardly begin the process of tracing a “blood line” back to the pre-Columbian age. The majority also leaves unanswered the question of how the racial make-up of a defendant’s more distant ancestors is to be determined, even assuming the highly questionable premise that sufficient “bloodline” evidence of his or her ancestors’ identities would reasonably be available.
A more flexible rule on the admissibility of expert cultural evidence would more closely comport with the general rule that expert testimony should be admitted when it will likely assist the trier of fact in arriving at the truth. United States v. Luschen, 614 F.2d 1164, 1169 (8th Cir.1980) (quoting Holmgren v. Massey-Ferguson, Inc., 516 F.2d 856, 857-58 (8th Cir.1975)). A trial court should be mindful that “it is now for the jury, with the assistance of vigorous cross-examination, to measure the worth of the opinion,” Singer Co. v. E.I. du Pont de Nemours & Co., 579 F.2d 433, 443 (8th Cir.1978), and not for the court to make that determination in the guise of a ruling on relevancy.
Moreover, it' would appear that the fundamental difference between the district court’s view, as affirmed by the majority, and my view, is the priority I would give to the basic principle that in a criminal proceeding a party should always have the right to have the jury pass upon the reasonableness of the theory of his or her case. Thus, the defendant should be able to come forward with any and all proof as to his cultural identity. Certainly it was important here that Curnew be allowed to testify that he was considered by himself and others to be a full blooded Indian, that his father’s mother was called an “old squaw” and spoke the Indian language, and that his mother’s father was called an “old Indian.” This testimony, along with whatever proof of cultural identity that the expert could add, would in my judgment create a fair inference for the defendant to argue to the trier of fact that he did not violate section 1326. There are many things within life’s experiences that cannot be proven to an absolute certainty. A statutory exemption to criminal prosecution should not require proof of that which cannot be proved. Under section 1359 Congress did not intend proof of the impossible.
The relevancy of Curnew’s proffered testimony should also be considered in light of his burden of proof on the issue of his Indian ancestry. Although Curnew submits his defense under section 1359 as an affirmative defense, the government nonetheless bears the ultimate burden to prove that he violated section 1326. Once Cur-new proffers testimony that he was exempt from section 1326 because he is an American Indian, then the burden of production by the defendant is satisfied. Cf. Stump v. Bennett, 398 F.2d 111, 118-20 (8th Cir. 1968) (burden of persuasion on government unaffected by assertion of alibi defense). In any case, whether Curnew was or was not exempt as a 50% blood Indian was a question of fact for the jury and not one of law for the court. It thus should be for the jury to decide the weight of the testimony offered by Curnew. Accordingly, I would conclude that the trial court abused its *1341discretion in excluding Curnew’s expert’s testimony and Curnew’s own testimonial evidence from the jury’s consideration.