Unfortunately, the top-scoring peptide for each spectrum determined by the search engines described in the previous section is not necessarily the correct identification. The remaining challenge is to determine whether the putative identification is in fact correct. Five years ago, the standard procedure was to apply an arbitrary score cutoff and manually inspect spectra and judge correctness. This was extremely labor intensive and subject to interpreter variability and thus not repeatable. Recently several main techniques have emerged for validating the search results and assigning a FDR for a given threshold.