British Terror Raid Based On Faulty Intel?

Questions are being asked in the aftermath of the British raid on a location in London that resulted in one person shot, and two people arrested in connection with an anti-terror probe. The problem is that the raid may have been based on faulty intel:

Senior counter-terrorism officials now believe that the intelligence that led to the raid on a family house last Friday in a search for a chemical device about to be used to attack Britain was wrong, the Guardian has learned.

Counter-terrorism officials were under pressure last night after days of meticulous search of the house in east London failed to produce anything to link the two men they arrested to a chemical plot. But a senior police officer said they had been left with "no choice" but to force entry into the house because there was specific intelligence of a threat to public safety.

One official, with knowledge why police acted and what had been found from days of searching, said the intelligence had been acted on correctly, but added last night: "There is no viable device at that house. There is no device being constructed, or chemicals. There does not appear to be anything there or anywhere else."

As lawyers for the two arrested men continued to protest their innocence, it emerged that the man who had passed the specific information that led to the raid in which a man was shot last Friday was a police informant who had been providing intelligence about the activities of alleged Islamist militants for several weeks.

This was despite previous reports quoting police sources that suggested the informant was being handled by the security service, MI5. It was the police who passed the information from the informant to MI5 officers to assess it, the Guardian understands. MI5 and police then agreed the information was specific and credible and made a joint decision it had to be acted upon immediately.

It is understood that attempts to corroborate the information were not made because of the perceived need to act quickly. "If there was an immediate risk to public safety, there would not have been time to bug the house," an intelligence source said. A counter-terrorism official said: "If the intelligence was right there was a serious risk to the public. We did not know if it was right or not until we went in." Another official added: "Intelligence is patchy. Even if it suggests a 5% likelihood of something nasty, we can't take that risk".

But what remains puzzling is the reliance on a single apparently uncorroborated source for information that prompted a high-profile mass raid which, even without the shooting of one of the men, would have provoked a strong reaction. Andy Hayman, the Met's assistant commissioner specialist operations, refused to apologise for the raid yesterday while admitting that so far officers had not found the specific item they were looking for - thought to be a chemical device - in the terraced house in Forest Gate which was the subject of a pre-dawn raid involving more than 250 officers, including armed teams and government scientists.

What is the acceptable level of risk? Are you willing to tolerate a 5% chance that a terrorist is actually planning on carrying out an attack with chemical agents with a single uncorroborated source as the basis for the intel? 1%?

Does it matter if the risk is .01% if you live in Terra Haute, IN, but 5% if you live or work in Manhattan, NY?

This situation once again notes the difficulty in obtaining intel and the difficulty balancing civil rights and security needs.