Double interrogation

Double interrogation is an interrogation method
that is used by some intelligence agencies.

The method consists of first interrogating a suspect via using
an infallible anticholinergic truth-serum drug, which also prevents long-term memory-formation,
such that the suspect tells the interrogator(s) everything that they know,
but does not remember having told the interrogator(s) any of it.
That is the first interrogation.

Next, the suspect is interrogated via "conventional" methods
which are intended to "break" the suspect,
such as sleep-deprivation, stress-positions, and/or waterboarding.
That is the second interrogation.
During the second interrogation, the interrogator(s) know
exactly what the suspect knows and doesn't know,
and knows if the suspect is telling the truth or lying.
It is the aim of the second interrogation to use those brutal methods
to obtain as much information as possible as they had obtained during the first interrogation.
This may additionally serve to test and refine their "conventional" methods,
to see what works best.

The most famous cases of people who were subjected to double interrogation
were the three Al-Qaeda members who were waterboarded by the CIA,
under the administration of George Tenet and Gina Haspel.
By the time that those three men were waterboarded,
the CIA had already extracted all of their information, unbeknownst to them.