Disclosed are apparatus and methods for inspecting a semiconductor sample. Locations corresponding to candidate defect events on a semiconductor sample are provided from an optical inspector operable to acquire optical images from which such candidate defect events are detected at their corresponding locations across the sample. High-resolution images are acquired from a high-resolution inspector of the candidate defect events at their corresponding locations on the sample. Each of a set of modelled optical images, which have been modeled from a set of the acquired high-resolution images, is correlated with corresponding ones of a set of the acquired optical images, to identify surface noise events, as shown in the set of high-resolution images, as sources for the corresponding candidate events in the set of acquired optical images. Otherwise, a subsurface event is identified as a likely source for a corresponding candidate defect event.