Plaintiff estopped from asserting patent after four year delay in filing suit where defendant invested in accused products during that time

"I hold as a matter of law that [defendant] suffered material prejudice because of plaintiff's [four year] delay in bringing suit. . . . As [plaintiff] did not follow through on its initial threat to sue, [defendant] continued investment in [the accused product] line. [Defendant] . . . invested in marketing [the accused products] and obtaining trademark protection. It increased its sales force and devoted a substantial percentage of its promotional resources to the products. . . . This uncontroverted evidence establishes a nexus between plaintiff's delay and [defendant's] expenditures related to [the accused products]."

Aspex Eyewear, Inc. et al v. Clariti Eyewear, Inc., 1-07-cv-02373 (NYSD November 26, 2008, Memorandum Decision)