JACKSON, Miss.—A Mississippi judge will decide whether a death row inmate who says he wants to be executed is mentally competent to waive all his appeals. The state Supreme Court on Thursday ordered the examination in the case of David Cox. Cox wrote to Mississippi Chief Justice Bill Waller Jr. in August saying he wanted to fire his lawyers, give up all his appeals and have the state Supreme Court set his execution date. “I seek in earnest to (waive) all my appeals immediately, I seek to be executed as I do here, this day, stand on MS death row a guilty man worthy of death—please grant me this plea,” Cox wrote in an Aug. 16 letter . Cox pleaded guilty to shooting his wife Kim in 2010 in the Union County town of Sherman, raping her daughter in front of her, and watching Kim Cox die as police negotiators …