If law-abiding citizens are to be protected against unjust persecution by the police, there must be two police forces and two Scotland Yards, one designed, as at present, to prove guilt, the other to prove innocence; and in addition to the public prosecutor there must be a public defender, of equal legal eminence. This is obvious as soon as it is admitted that the acquittal of the innocent is no less a public interest than the condemnation of the guilty.
Source: Power, 1938.
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