No, think again! If you asked me that last month, I would have told you that the core cases on a Shepard’s® and KeyCite report would be roughly the same, although not identical. But a new empirical study just came out showing just how wrong that conventional wisdom is. The author found that even though both systems use computer algorithms to generate the results:
…Shepard’s is finding twice as many unique relevant results as KeyCite, but it is not finding all of the relevant results… It was surprising how few cases each citation system had in common…
The takeaway: definitely use both Lexis and Westlaw when you are trying to identify all relevant cases, and if you don’t have access to both then make sure to run some redundant searches in the cases database.
Source: Susan Nevelow Mart, The Case for Curation: The Relevance of Digest and Citator Results in Westlaw and Lexis. Available on SSRN and forthcoming in Legal Reference Services Quarterly.