A、terrorists among the detainees could not be found out. B、interrogators in the prison would abused and tortured the detainees.

The U.S. lawmakers witnessed interrogations, toured cellblocks and ate the same lunch given to detainees on the first congressional visit to the prison for suspected terrorists since criticism of it intensified in the spring. A Senate delegation also was visiting this weekend.
   "The Guantanamo we saw today is not the Guantanamo we heard about a few years ago," said Rep. Ellen Tauscher.
   Still, lawmakers from both parties agree more still must be done to ensure an adequate legal process is in place to handle detainee cases. In the meantime, said Rep. Joe Schwarz, "I think they’ re doing the best they can to define due process here."
Republicans and Democrats alike fear the prison at the U.S. Navy base in eastern Cuba is hurting the United States’ image because of claims that interrogators have abused and tortured inmates. The White House and Pentagon say conditions are humane and detainees are well-treated.