Jewish law presents some conflicting principles that effect how Jews view torture. According to Jewish law, one is permitted to defend oneself by killing an attacker if one's life is immediately threatened. In the case of a rodef, a pursuer, Jewish law teaches: When one pursues another with intent to kill every Jew is commanded to save the intended victim, even at the cost of the pursuer's life (Mishneh Torah, Rotzeach 1:6.). It is arguable that a suspect who possesses information that could lead to the prevention of a terrorist attack is a rodef, and therefore the community has the responsibility to use whatever means are its disposal to extract that information. Similarly, the rule of pikuach nefesh requires breaking most laws (except murder, idolatry and sexual crimes) to save a life, but only when the threat to life is imminent. These principles have led some to argue that torture may be necessary to prevent an immediate threat to human life.
At the same time, we cannot know for sure whether an individual is truly a rodef until after an interrogation. Furthermore, Judaism teaches that everyone, even the prisoner, is created b'tzelem elohim (in the image of God) and is entitled to be treated with dignity and respect. Not only is torture a clear violation of this principle, experience has taught that there are more effective ways of extracting information from detainees that do not reach beyond the bounds of law.
Furthermore, our tradition teaches "if someone attacks another, the second is innocent of any responsibility for injury caused to the first, since he has a right to defend himself, but if he was able to use less force but caused greater injury then he is guilty" (Shulchan Aruch). Torture inflicts more physical and psychological harm than other interrogation techniques which are, in fact, more effective means of obtaining crucial national security intelligence and therefore cannot be condoned by Jewish law.
In 1999, the Supreme Court of Israel ruled that although the war on terrorism requires interrogation of suspected terrorists, torture and physical force must not be used. Israeli Supreme Court Justice Aharon Barak wrote:
This is the destiny of a democracy -- it does not see all means as acceptable, and the ways of its enemies are not always open before it. A democracy must sometimes fight with one hand tied behind its back. Even so, a democracy has the upper hand. The rule of law and the liberty of an individual constitute important components in its understanding of security. At the end of the day, they strengthen its spirit and this strength allows it to overcome its difficulties.
For a more detailed discussion of torture and Jewish values, see the Central Conference of American Rabbis' 2005 Resolution on the Use of Torture and Other Forms of Coercion to Obtain Information from Prisoners as well as Rabbis for Human Rights - North America's "Rabbinic Resources on the Jewish Values and the Issue of Torture".
Resolution on Torture (2005)