# An Alpha-based Prescreening Methodology for a Common But Unknown Source Likelihood Ratio with Different Subpopulation Structures

#### Abstract

Prescreening is a commonly used methodology in which the forensic examiner includes sources from the background population that meet a certain degree of similarity to the given piece of evidence. The goal of prescreening is to find the sources closest to the given piece of evidence in an alternative source population for further analysis. This paper discusses the behavior of an $\alpha-$based prescreening methodology in the form of a Hotelling $T^2$ test on the background population for a common but unknown source likelihood ratio. An extensive simulation study with synthetic and real data were conducted. We find that prescreening helps give an accurate estimate of the likelihood ratio when there is a subpopulation structure in the alternative source population.

Feb 8th, 1:00 PM

An Alpha-based Prescreening Methodology for a Common But Unknown Source Likelihood Ratio with Different Subpopulation Structures

Volstorff A

Prescreening is a commonly used methodology in which the forensic examiner includes sources from the background population that meet a certain degree of similarity to the given piece of evidence. The goal of prescreening is to find the sources closest to the given piece of evidence in an alternative source population for further analysis. This paper discusses the behavior of an $\alpha-$based prescreening methodology in the form of a Hotelling $T^2$ test on the background population for a common but unknown source likelihood ratio. An extensive simulation study with synthetic and real data were conducted. We find that prescreening helps give an accurate estimate of the likelihood ratio when there is a subpopulation structure in the alternative source population.