Legal Memorandum: Motion to Amend a Complaint

Issue: Under federal law, how do courts determine whether there was undue delay on the part of the plaintiff when seeking to add new or additional defendants?

The fact that a plaintiff could have brought claims against a defendant earlier is only one factor for the court to use in exercising its discretion on a Motion to Amend.  It is not determinative by itself.  See Castleglen Inc. v. Resolution Trust Corp., 984 F.2d 1571, 1585 (10th Cir. 1993) (citing several factors).  The Tenth Circuit has noted that prejudice is the "most important factor."  Velocity Press v. Key Bank, N.A., 570 F. App’x 783, 788 (10th Cir. 2014) (citing Minter v. Prime Equip. Co., 451 F.3d 1196, 1207 (10th Cir. 2006)). 

Moreover, the fact that a plaintiff erred in not including the proposed new defendants in the original complaint cannot, by itself, be a sufficient ground for denying the amendment.  Indeed, just such a mistake is a requirement, not a disqualification, for allowing an amendment to relate back to the time of the initial complaint. See Fed. R. Civ. P. 15(c)(1)(C)(ii); Krupski v. Costa Crociere S.p.A., 560 U.S. 538, 550 (2010). .

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