Colonel Parrish presided over the case of Staff Sergeant Alberto Martinez, a GI who was accused of murdering two officers with a grenade.
[8][9] On May 29, 2008 Colonel Peter Brownback, the Presiding Officer over Omar Khadr's Guantanamo military commission was removed, and Parrish was appointed to take his place.
Lieutenant Commander William Keubler, one of Khadr's Defense attorneys, speculated that Brownback's unexpected replacement was due to his insistence that the Prosecution complete the process of discovery, before he set a trial date.
Keubler said the dispute arose because Masciola wanted to continue to play a role in modified commissions, moved to the continental United States, while Keubler wanted to see the charges against Khadr dropped, and see him repatriated to a kind of parole—rehabilitation program in Canada.
In late May Parrish scheduled a hearing for June 1, 2009—even though Obama's suspension was still in effect, to consider the issue of whether Keubler should be allowed to continue to represent Khadr.