Read this excellent essay on French torture in Algeria. You’ll need to watch an ad in order to get to it.
I’ve always been a little bit twitchy about torture; it must serve some purpose to authorities, because it’s been around forever (functionalism alarm). Rejali makes the point that torture does not work by increasing available intelligence; it may actually decrease actionable intelligence, bits that can lead to actual arrests. Instead, torture simply destroys enemies of the regime. Whereas The Battle of Algiers shows the French successfully torturing Algerians for information, Rejali argues that the French tortured indiscriminately, wiping out the base of the FLN while at the same time destroying any possible basis for future political agreement between the Algerian population and the French authorities. I don’t think that Pontecorvo makes this connection in the film, but it’s arguable. Moreover, the impact on the torturer is almost as grim as the impact on the victim.