Project managers can use capture-recapture models to manage the inspection process by estimating the number of defects present in an artifact and determining whether a reinspection is necessary. Researchers have previously evaluated capture-recapture models on artifacts with a known number of defects. Before applying capture-recapture models in real development, an evaluation of those models on naturally-occurring defects is imperative. The data in this study is drawn from two inspections of real requirements documents (that later guided implementation) created as part of a capstone course (i.e. with naturally occurring defects). The major results show that: a) estimators improve from being negatively biased after one inspection to being positively biased after two inspections, b) the results contradict the earlier result that a model that includes two sources of variation is a significant improvement over models with one source of variation, and c) estimates are useful in determining the need for artifact reinspection.