Methods and systems for determining a layer on which a defect detected on a wafer is located are provided. One method includes detecting defects on a wafer by directing light to the wafer at first and second angles of incidence and determining locations of the defects on the wafer based on the output corresponding to the defects. For one of the defects detected in the output generated for one spot illuminated on the wafer with the light directed to the wafer at the first and second angles, the method includes comparing the locations of the one of the defects determined based on the output generated with the light directed to the one spot on the wafer at the first and second angles. The method further includes determining a layer of the wafer on which the one of the defects is located based on results of the comparing.