A recent invention, the paid police force dates from 1829 in the UK, although it was familiar before then in France, Russia and elsewhere. It rapidly grew in power and complexity, and is now considered to be necessary almost everywhere and by almost everyone. Its powers vary from place to place, and in accordance with the political structure; being the instrument to enforce the law, its nature is partly determined by the character of the law that it enforces.
The following variables should be noted:
(i) extent, i.e. the quantity of policemen per head of population;
(ii) powers, e.g. powers of search, with or without warrant, of arrest, detention, interrogation and restraint;
(iii) provisions for redress; to what extent may the citizen (de jure), and to what extent can he (de facto) obtain redress (e.g. through a controlling body, or a court of law) against a police officer who has acted ultra vires?;
(iv) openness; to what extent can the police operate secretly, and in such a way as to penetrate the private life of the citizen? (See police state);
(v) armaments; what weapons may the police use in enforcing the law, and when?
It is necessary to distinguish those systems which provide for constant active invigilation of the police, and those which merely provide redress for violations. Given the power which, on one plausible view, the police must possess in order to fulfil their function, it may be that legal provisions for redress are insufficient, in that they do not override the powers of intimidation which the police can bring to bear on any potential complainant. For this reason there have evolved, in many Western countries, commissions of inquiry which attempt to invigilate independently, and also to prevent abuses before they have become widespread. In English common law, unlawful arrest and imprisonment have from early on been crimes, and since 1967 a distinction is made between ‘arrestable offences’ and ‘non-arrestable offences’ (where arrest requires a warrant), in order to curb police powers while replacing the traditional distinction (still upheld in the US) between ‘felonies’ and ‘misdemeanours’.