Not even the support of Oklahoma's attorney general may be enough for 25-year death row inmate Richard Glossip to obtain a new murder trial judging from the tenor of his hearing at the U.S. Supreme Court on Wednesday.

The argument at the high court was perhaps Glossip's best and last hope to be spared from the execution chamber following roughly a quarter century of trials, appeals and hearings. His latest bid centers around claims that his 2004 conviction for the murder of Oklahoma City motel owner Barry Alan Van Treese was tainted by prosecutorial misconduct and long-hidden exculpatory evidence.