What is the defense of laches?

We need give little time to a discussion of the defense of laches, though it is quite difficult to find in the testimony anything to justify or excuse the long delay in bringing the action, especially as the bonds on their face referred to the mortgage which was recorded in the proper offices in Louisiana whereby notice was given to all holders. We much incline to think that this defense also should be sustained, but prefer rather to base our decree upon the statute of limitation. As to the defense of laches we think consideration may helpfully be given to O'Brien v. Wheelock, 184 U.S. 450, 493, 22 Sup.Ct. 354, 46 L.Ed. 636. The court, during the trial, was purposely very liberal in the admission of testimony, especially when offered by the plaintiff, preferring to be free to give it any weight it might be entitled to rather than to exclude it altogether. But while dealing with the question of admissibility in that spirit, some few items of proffered testimony seemed to be so remote as to fall outside of any reasonable limit.