Despite the attention of many studies, researchers still struggle to identify criteria with which to sex juvenile remains at levels of accuracy and reproducibility comparable with those documented for adults. This study uses a sample of 82 juvenile ilia from an identified Portuguese population (Lisbon collection) to test the cross-applicability of a new approach by Wilson et al.  that uses geometric morphometric methods to sex the subadult ilium. Further, we evaluate the wider applicability of these methods for forensic casework, extending the age range of the original study by examining an additional 19 juvenile ilia from the St. Brides and Spitalfields collections, housed in London. Levels of accuracy for the Portuguese sample (62.2–89.0%) indicate that the methods can be used to document dimorphism in another sample. Discriminant functions are sample-specific, indicated by not better than average classification using cross-validation. We propose a methodological update, whereby we recommend disuse of the auricular surface morphology criterion, based upon reduced success rates and inadequate accuracy of female identification. We show, in addition to population differences, differences in the ontogeny of dimorphism may lead to differing degrees of success for female identification using some criteria. The success rates are highest between the ages of 11.00 and 14.99 years (93.3% males, 80.0% females).