And how would an officer in the field determine this question upon arresting a suspect?

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Previously officers were required to issue a summons before arresting a suspect.

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At U.S. borders or when arresting a suspect, for instance, police and government officials have argued that no such warrant is required.

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But even as Austrian authorities were arresting a Serb suspect last month, they were also playing host to Mr Hussein's deputy, Izzat Ibrahim al-Douri, before letting him go home safely to Iraq.

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Senior British police sources say they were rushed into arresting the plotters because a related suspect, Rashid Rauf allegedly al-Qaeda's linkman had been unexpectedly arrested in Pakistan at America's behest.

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