A set of trigrams can be generated for each document in a plurality of documents processed by an e-discovery system. Each trigram in the set of trigrams for a given document is a sequence of three terms in the given document. A set of trigrams for each similar document is then determined based on the set of trigrams for the original document. To facilitate identification of the similar documents, a full text index is then generated for the plurality of documents and the set of trigrams for each document are indexed into the full text index, as individual terms. Queries can be generated into the full text index based on trigrams of a document to determine other similar or near-duplicate documents. After a set of potentially similar documents are identified, a separate distance criteria can be applied to evaluate the level of similarity between the two documents in an efficient way.