Also known as: DNA profiles · DNA profiling · genetic profile · DNA fingerprint
Written by attorneys · grounded in primary & secondary sources — see below
A collection of length measurements for variable number tandem repeats at multiple chromosomal locations that together characterize a biological sample or individual.
Dominic Drake was charged with assault after an attack in a hospital garage. State analyst Dr. Moore compared a DNA profile generated by an out-of-state lab from skin cells under the victim's fingernails to a profile her own lab produced from Drake's blood. She testified that the profiles matched at multiple loci and offered her independent opinion identifying Drake as the source. The out-of-state profile itself was never admitted into evidence.
Delilah Duran brought a paternity action against Darius Dixon. The state laboratory used six polymorphic probes on samples from the child, Duran, and Dixon. Visual comparison of the resulting autoradiographs showed that Dixon's DNA profile included all bands present in the child's profile at each genetic system tested. Statistical analysis under Hardy-Weinberg equilibrium then produced a paternity index supporting Dixon's inclusion as the biological father.
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An expert may rely on such a profile when it is used only to explain the basis of the expert's independent opinion and is not offered for its truth. The profile also must not have been prepared primarily to accuse a targeted individual. Under these conditions the Confrontation Clause is not implicated because the jury evaluates the testifying expert's own analysis.
A DNA profile consists of the measured lengths of variable number tandem repeats at several specific chromosomal locations. Laboratories obtain these lengths through probes that mark DNA fragments and produce an autoradiograph whose band pattern is read as the profile. The resulting set of lengths serves as the identifying characteristic of the sample.
After visual inclusion is confirmed across multiple genetic systems, laboratories apply population-genetics principles such as Hardy-Weinberg equilibrium to calculate a paternity index or random-match probability. The calculation uses databases of VNTR frequencies drawn from relevant racial or ethnic groups. The resulting statistic quantifies the rarity of the observed profile in the population.
…protection to defendants. The expert in this case was well qualified and provided her own independent opinion based on the two DNA profiles. This is consistent with the way expert testimony has traditionally been admitted in our courts. Dissenting opinions Dissenting — Kagan, J. Justice Kagan, with whom Justice…