User blog comment:Imhungry4444/One Piece Chapter 690 Review/@comment-5145405-20121129004438

I think Law knew he was going to use his uber attack and possibly even destroy the SAD production room for multiple reasons. 1. Law isnt stupid, he wouldnt recklessly destroy the SAD production room if his objective was to obtain the SAD. It is more likely that he wanted to halt the production of SAD. 2. At the beginning of the counter attack he gave G5 and the Stawhats limited time to complete their objectives because the lab would become unsafe. The lab is now exposed to Shinokuni making it unsafe. Cutting Vergo in half was a bonus for him.