The psychologist who helped develop the C.I.A.’s “enhanced interrogation” program during the Bush-era testified for the first time to the court at Guantánamo Bay on Tuesday, facing five men who had been subject to his brutal techniques. James E. Mitchell defiantly testified in front of the former Guantánamo detainees who reportedly underwent his program of violence, sleep deprivation, and humiliation. Among the defendants was Khalid Shaikh Mohammed, who is charged with helping to plot the Sept. 11 attacks and was personally waterboarded by Mitchell 183 times. Mitchell reportedly worked as a contractor for the intelligence agency and helped create what the government called “enhanced interrogation techniques,” which amounted to torture. Mitchell appeared at a pretrial hearing for the men facing charges in the 9/11 attack. They are reportedly seeking to have the court discard statements they made to the C.I.A. in Guantánamo, claiming that they were conditioned to tell them what they wanted to hear during interrogations. Mitchell said the accusations are “untrue and malicious,” adding that he only made an appearance at the court to testify in person in front of the 12 relatives of the 9/11 victims and their companions.