Abstract:
Defining the relevant population to sample is an important issue
in data-based implementation of the likelihood-ratio framework
for forensic voice comparison. We present a logical argument
that because an investigator or prosecutor only submits suspect
and offender recordings for forensic analysis if they sound
sufficiently similar to each other, the appropriate defense
hypothesis for the forensic scientist to adopt will usually be that
the suspect is not the speaker on the offender recording but is a
member of a population of speakers who sound sufficiently
similar that an investigator or prosecutor would submit
recordings of these speakers for forensic analysis. We propose
a procedure for selecting background, development, and test
databases using a panel of human listeners, and empirically test
an automatic procedure inspired by the above. Although the
automatic procedure is not entirely consistent with the logical
arguments and human-listener procedure, it serves as a proof of
concept for the importance of database selection. A forensicvoice-
comparison system using the automatic database-selection
procedure outperformed systems with random database
selection.
