Then what would be the next best thing?
I think the answer would be a near perfect lie detection system.
Imagine that whenever any operative or associate of any terrorist organization got into custody
he/she easily tells everything and answers all questions truthfully.
Wouldn't that be an immense help for law enforcement people?
Then the question is if a near perfect lie detection system really possible or not?
I think the answer must be yes with technology of today.
The main tech of today that can help is AI.
Today AI systems are getting even better than human experts for analyzing all kinds of data, text, image, video.
What needs to be done is to use as many different sensors as possible (heart rate, EEG, speech (voice stress), even brain scans,...)
and train an advanced deep learning AI system to detect lying.
Of course if it succeeds and nobody can find a way to beat it then all subjects would try to stay silent.
But I believe that problem maybe solvable using so called "Truth Serum" chemicals which makes a person talkative.