Is a Rare Genetic Variant Present at the Crime Scene Admissible As Testimony After Statistical Analysis ?
In People v. Contreras, 246 Ill. App. 3d 502, 508, 615 N.E.2d 1261, 1266, 186 Ill. Dec. 204 (1993), a forensic geneticist testified that electrophoresis testing on samples taken from the defendant revealed a rare genetic variant that was likewise present in the crime scene evidence.
In turn, population statistics databases were used to determine the frequency with which the variant occurred in the male Mexican-American population, of which the defendant was a part.
The court upheld the admission of this testimony based on the threshold reliability of the population statistics databases. Contreras, 246 Ill. App. 3d at 511, 615 N.E.2d at 1268.
The use of population statistics databases thus evolved out of the necessity to estimate the random match probability of a possible source of a DNA profile occurring within the appropriate reference population.
As the Illinois Supreme Court recognized in People v. Miller, 173 Ill. 2d 167, 184-85, 670 N.E.2d 721, 730, 219 Ill. Dec. 43 (1996).
"For a match to be meaningful, a statistical analysis is required.
The statistical analysis determines the frequency in which a match would occur in a database population." Miller, 173 Ill. 2d at 185, 670 N.E.2d at 730.
The identity of the other profiles in the database is of no significance in calculating these random statistical probabilities.