I appreciate Liz's post because every once in a while I get sympathetic to the idea that passive surveillance might be a reasonable price to pay for increased security. But obviously if it doesn't work, then there is clearly no justification for it.

On a related point, I sometimes think there may be some value in a domestic intelligence service to pursue terrorists. The problem with relying solely on the FBI to do this job is its law enforcement focus--it is necessarily concerned with gathering evidence in such a way that it can be presented in court. But I can see times when all we want is the information--say about a looming attack--even if it means collecting it in a way that would be inadmissible in court.

Britain has an agency that does exactly this: MI5. It is separate and supplementary to Britain's version of the FBI, Scotland Yard. Both agencies have had long and deep experience with terrorism in that country owing to the Irish problem. Therefore, one would think that they would be far more effective than the FBI in preventing terrorist incidents. Yet London has not been spared Islamic terrorist incidents, while we have had none since 9/11.

My point is that if there were clear and demonstrable evidence that sacrificing our liberties to pervasive video surveillance and a domestic spy agency were effective then it would be reasonable to consider those options. But if they have no record of effectiveness in a country with considerable experience using them, then the case for moving in that direction becomes nonexistent.

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