1. A spoken language understanding system comprising: a processor; a first module configured to control the processor to classify a set of labeled candidate utterances based on a previously trained classifier and generate classification types for each candidate utterance, each classification type having a respective confidence score; a second module configured to control the processor to sort the candidate utterances based on an analysis of the confidence score of each candidate utterance compared to a respective label of the candidate utterance, wherein the analysis is based at least in part on a Kullback-Liebler divergence; and a third module configured to control the processor to recheck candidate utterances according to when the Kullback-Liebler divergence is greater than a threshold.