Existing forensically-relevant databases
The field has one large, forensically-relevant database specifically for Southern Standard British English (SSBE). The Dynamic Variability in Speech Corpus (DyViS; Nolan et al., 2009) was completed in 2009 and has already provided a wealth of previously unavailable population data (including: Kavanagh, 2013; Gold et al., 2013; King et al., 2013; Gold, 2014; Wood et al., 2014; Earnshaw, 2014; Hughes in progress), and a number of these population statistics have already been cited in UK court cases (Professor Peter French, personal communication).
A few smaller forensically-relevant databases also exist, but these do not contain enough speakers or speech material on which to draw robust population statistics (e.g. Fecher, 2012; Brown and Wormald, 2014; McDougall, 2014).
Effectively, this means that the DyViS database is the sole resource for robust forensic research, which leaves the field with an incomplete representation of all accents; this is especially true given that SSBE is not representative of all British English speakers (in reality only a small minority). For instance, there are no large, forensically-relevant databases for any Northern British English accents, meaning that FSC cases involving Northern British English speech do not have adequate population data to consult.