A psychologist used as a key government witness in death row cases in Texas has reached a settlement barring him from performing future evaluations. George Denkowski agreed to the deal after his methods came under challenge. Denkowski has been accused of helping prosecutors unfairly send mentally retarded prisoners to death row. Defense attorneys are planning to seek appeals court reviews of at least 14 death row cases that relied on Denkowski’s testimony. But the settlement says that it cannot be used as evidence in cases that are retried.