Mark Leonard, his half-brother Bob Leonard, Jr., Monserrate Shirley, Gary Thompson and Glenn Hults are all charged in connection with the November 2012 house explosion.
Prosecutors say he was part of a conspiracy behind the explosion in the Richmond Hill neighborhood that killed Dion and Jennifer Longworth and damaged nearly 80 homes in November 2012.
Glenn Hults was charged with conspiracy to commit arson in connection with the explosion.
The decision came as Gary Thompson, 44, appeared in court Wednesday for the second time since his arrest in January.
Mark Leonard wants to prevent jurors from hearing any statements made to investigators by his brother, Bob Leonard, Jr.
Bob Leonard is accused, along with his brother Mark, Monserrate Shirley and Gary Thompson of setting the explosion at Richmond Hill in November 2012.
It's not known if Leonard will remain in Allen County or be brought back to Marion County until that September hearing.
Court records obtained by I-Team 8 show Allen County Judge Frances Gull was appointed to Bob Leonard's case Friday.
A judge has rejected several potential defense strategies made by attorneys for one of the suspects in the 2012 south side explosion case. Mark Leonard’s trial will not be split into two parts, nor will witness testimony be consolidated, according to court documents obtained by I-Team 8.
As I-Team 8 first reported Thursday, Bob Leonard's trial will be held in Fort Wayne.