Military commissions also make it easier to introduce statements that are the product of coercive interrogation.
Technically, the prosecution can introduce statements made by any individual or organization named as an unindicted co-conspirator without such statements being dismissed as hearsay.
The government also did not introduce statements Mr. Ghailani made before he was brought into the civilian system, even though prosecutors said they amounted to a confession.
Prosecutors wanted separate trials for the men, Michael Hamlin and Percey Jordan, because the United States attorney's office plans to introduce statements from each man that will implicate the other.
Normally such a warning is necessary if prosecutors want to introduce statements made by a suspect in custody as evidence in court, but the administration said it was invoking an exception for questions about immediate threats to public safety.
Prosecutors introduced statements at the trial from the depositions of former Interior Ministry officials and from Mr. Mubarak's former intelligence chief, Omar Suleiman, to show that the ministry could never have given an order to shoot protesters without presidential authorization.
The defense introduced statements from former C.I.A. officials who said that they knew that Blackwater had been acting at the agency's direction, and filed motions seeking documents and evidence of the C.I.A.'s role in the weapons deals.
The court strengthened the constitutional right of criminal defendants to confront the witnesses against them, unanimously ruling that prosecutors cannot introduce statements from an absent witness -- on tape, for example -- unless the defense has had a chance to cross-examine the witness at an earlier hearing or a previous trial.
Cesar Gonzalez, a lawyer for Mr. Santiago, said introducing the statements at trial instead of having Mr. Edwards testify himself would impinge upon his client's Sixth Amendment right to examine witnesses.
When you start introducing conditional statements into the equation, it very quickly complicates things.
