User blog comment:Gourgeist/Shingeki no Kyojin Chapter 66 Review: Wish/@comment-3578577-20150210213348/@comment-99.120.99.33-20150406184149

My guess is no. Grisha may have been from outside the wall sent by his leader to infiltrate Humanity living within the walls and created the serum while in there.

I'm also guessing that the leader outside of the walls could be of Ackerman blood, angered with the Reiss family in how his(or her) family along with their allies in the Asian Clans had been treated by the royal family after years of loyal service.