Unfortunately none of the three techniques you mention is particularly
reliable. :/ Lie detectors can often detect when somebody is trying to
hide something, but they only work on people whose mental and emotional
reactions are relatively normal. Somebody who lacks the capacity to
feel guilt or a conscience (such as a psychopath or sociopath), or
somebody whose memory or ability to recognize reality is impaired (such
as a PTSD victim or a schizophrenic), isn't usefully testable by this
method.
Even relatively normal people often test as lying or guilty when they're
innocent. The real use of lie detectors is as a rough classifier that
sorts between people who can be reliably deemed innocent of any
knowledge or guilt about the matter whatsoever, and everybody else. The
problem with using it is that most people don't understand what a lie
detector is and its limitations, and assume that somebody who fails a
lie detector test is necessarily guilty.
I'll let you look up the medical literature on sodium pentothal.
Suffice it to say that it is sometimes helpful to question a cooperative
person, but is not reliable when questioning somebody who does not
cooperate.
Hypnosis is even less reliable as a tool for getting at the truth
because it places the subject in a state where the interrogator can
(often unwittingly) convince the patient that something is true when it
isn't. Do you remember the scandal associated with a number of child
sexual abuse cases where "recovered memories" were later proved to be
false by hard, objective evidence? For example, the McMartin preschool
case?
I've undergone hypnosis myself. It is an extremely effective tool for
pain management, but it works by teaching one part of your mind to
ignore or not notice input from another part of your mind. To this day
I have double memories of the surgery that saved my eyesight. I
remember the whole process, know in my mind that it was quite painful,
but either did not feel or did not notice the pain at the time or have
completely forgotten having done so. While I think that this was a good
thing and a proper use of the technique, it also altered my memories and
emotions through something that was effectively a lie.
I would be *extremely* hesitant to trust hypnotically retrieved
memories. It is simply too easy for the hypnotherapist's beliefs to
become the patient's memories, even when they both mean to get at the truth.
If there were a medical or other technique that reliably got at the
truth in this sort of situation, I'd be entirely in favor of using it.
(OK, assuming it did not do other irretrievable harm.) As best I know,
there isn't. So we're stuck with the fact that there are sometimes
cases when a third party cannot know the truth of a matter beyond a
reasonable doubt.
I hope that this trial will end with a conclusive finding of "guilty
beyond a reasonable doubt" or "these charges are clearly and
convincingly false", not something in-between. Any other finding leaves
both parties in limbo, a terrible outcome.