Looksmart Group, Inc. v. Microsoft Corporation, 4:17-cv-04709

Looksmart sued Microsoft for patent-related claims; after claim construction, Microsoft sought leave to amend its invalidity contentions.
The Court issued a claim construction order largely adopting Looksmart’s proposed constructions.
Microsoft argued the Court’s constructions justified amending its invalidity contentions and asked for leave post-claim construction.
Looksmart opposed in part, asserting Microsoft was not diligent under Patent Local Rule 3-6.
The scheduling order contained a fact discovery cutoff; Microsoft filed its motion over six months after the parties’ joint claim construction statement.
The Court denied Microsoft’s motion to the extent opposed, finding lack of diligence and therefore not reaching prejudice; Microsoft was ordered to serve amended contentions consistent with the order by a set date.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Microsoft acted with diligence in seeking to amend invalidity contentions	Microsoft was not diligent and waited too long after disclosure of competing constructions	Microsoft waited reasonably given the Court’s claim construction and reliance on its own constructions to craft invalidity theories	Court held Microsoft was not diligent and denied the motion to the extent opposed
Proper trigger date to measure diligence (date of parties’ joint proposed constructions vs. date of court’s claim construction order)	Measure from the date parties exchanged proposed constructions (earlier date)	Measure from the date of the Court’s claim construction order (later date) because the Court adopted Looksmart’s constructions	Court measured diligence from the date parties submitted the joint claim construction statement and found Microsoft’s 6+ month delay unduly long
Whether prejudice analysis is required if diligence is lacking	No, diligence is threshold; lack of diligence obviates need to address prejudice	Sought to show lack of prejudice given short/limited amendments and schedule	Court declined to analyze prejudice because Microsoft failed to show diligence

O2 Micro Int’l Ltd. v. Monolithic Power Sys., Inc., 467 F.3d 1355 (Fed. Cir. 2006) (if movant lacks diligence, district court need not address prejudice)
Word to Info Inc. v. Facebook Inc., [citation="700 F. App'x 1007"] (Fed. Cir. 2017) (discusses measuring diligence from date of disclosure versus date of court order in claim-construction-driven amendments)