Ethical use of torture evidence?
The case involves ten foreign nationals that have been detained under special post-9/11 legislation that have appealed against their confinement. They were confined because foreign intelligence services provided information about their links to international terrorism (read Al Qai'da). The lawyers for the detainees suggested that the evidence should be thrown out because it might have been obtained through torture.
However the lawyers have presented no evidence that any torture was used to obtain the information because they don't know even what the evidence is. The British government knows what the evidence is but has no reasonable way of knowing whether torture was used. Asking the foreign intelligence service whether torture was used satisfies nobody because the foreign intelligence service will always deny it. So to require the British government to only use non-torture evidence will make no difference to the use of torture. As such, it is a bad rule. That is why the Appeal Court ruled that any evidence can be used so long as British agents had not procured or connived at obtaining it through torture.
The rule is also far stronger than the Guardian depicts it. If the British sent a High Value Detainee to Central Asia knowing that he'll be beaten with rubber hoses or worse, then any evidence from that detainee is inadmissable. And because the British intelligence services are intensely bureacratic (as revealed by the Butler and Hutton enquiries), there will always be a paper-trial showing what was done to the proper authorities.
So what can be done about torture? Besides the obvious human rights consideration, there are practical objection to torture in that the quality of evidence is less reliable than that obtained through standard police methods or through stress methods. Pratically the best option is to send police officers and intelligence agents to train the intelligence services of dubious places in investigative methods and instilling a sense of professionalism. But this doesn't play well in the media.