CCTV UK Parliament（中央电视台英国议会）.pdf

April 2002 Number 175CCTVClosed Circuit Television (CCTV) surveillance of publicareas, such as car parks, housing estates and towncentres is increasingly commonplace. For example, 260cameras monitor the boundaries of the Parliamentaryestate. Recently, the Home Office allocated £170million to fund public area CCTV schemes in Englandand Wales. This has prompted debate over whetherCCTV surveillance reduces crime and whether currentlegislation appropriately regulates its use. This briefingdescribes how CCTV is used and examines issues suchas its effectiveness, civil liberties and its use in court.How CCTV systems are usedPublic and private CCTV schemes can be deployed for anumber of reasons:• Monitoring public areas to detect incidents and to co-ordinate police responses. CCTV is also used as an aidfor enforcing exclusion orders (where an offender isbarred from an area) - see box opposite.• Recording events for use as evidence and to informinvestigations. For instance, on the boundaries of theParliamentary estate, police on patrol alert CCTVoperators of incidents via radio links. CCTV operatorsthen record incidents as they unfold.• Directed surveillance of suspected offenders.• Deterrence of criminal activity – although the evidencefor this is inconclusive (see page 2).Information managementCCTV control rooms may deal with information frommany cameras. ‘Smart’ technologies can alert operatorsto pre-determined people, registration numbers orincidents, reducing the need for CCTV to be constantlymonitored (see automatic monitoring box on page 2).However the effectiveness of these systems dependsupon the reference information (e.g. licence platedatabases) being accurate and up to date.Most CCTV systems in the UK rely on analoguerecordings using standard videotape. However, digitalrecording is expected to dominate the industry within thenext 5 years. Although concerns arise over the potentialmanipulation of digital images and difficulties withviewing them in court (see page 4), digital recording hasa number of advantages over analogue recorders:• it greatly facilitates automated image searches• it allows easy logging of operator actions ensuringcorrect and appropriate use of cameras• systems are self-cleaning, removing the need toclean and replace analogue tapes manually• digital tapes can be more easily stored and reusedmore often.CCTV and Enforcement: Case StudiesManual identification of offenders in AccringtonAccrington’s 26-camera CCTV scheme is controlled from thelocal police station and operators are linked via radio withpolice and retailers. The town’s small population (30,000)means that operators gain knowledge of local offenders andcan identify them. Also, police provide photographs ofconvicted shoplifters excluded from retail outlets and CCTVoperators monitor for any breaches. During the first year,there was a drop in shoplifting, criminal damage and theftfrom motor vehicles, with little sign of crime displacement toadjacent areas. However, it is unclear the extent to whichCCTV is responsible for these effects, as other crimereduction measures were introduced concurrently.Automatic face recognition systems in NewhamSince 1998, Newham (pop. 235,000) has piloted facerecognition software. Images are compared against a police‘watch-list’, which is authorised by a senior police officer, ofapproximately 100 convicted offenders wanted for arrest orconsidered likely to re-offend. CCTV operators are privy onlyto the personal data that is necessary for this purpose. Anoperator verifies matches made by the software and for falsealarms the CCTV image is deleted. The system is highlypublicised to deter crime; youths placed on the list are takento view the system’s capabilities. Crime in CCTV areas hasdropped by an average of 35%, but motor vehicle crime inthe surrounding non-CCTV areas has risen by 10%. Crimesagainst property have risen and crimes against people havebecome less common. However, again it is not possible toidentify how far these effects are directly attributable toCCTV use, as other crime reduction measures (munity wardens) were introduced alongside.postnote April 2002 Number 175 CCTV Page 2Automatic MonitoringAutomatic face recognitionThe police can photograph anyone detained, convicted orcharged with an offence. Automatic systems are availablethat can correlate CCTV images with digital databases ofphotographs. In controlled conditions these systems canachieve accuracy of 96%, but covert face recognition islikely to be less effective. Obtaining clear facial images isdifficult due to factors such as lighting, movement andaccessories such as hats or glasses that obscure the face.Chances of a false match increase with the size of thephotograph database (this is why the Newham scheme usesa small database of images).Automatic Number Plate Recognition (ANPR)ANPR systems read number plates picked up by CCTV andmatch them against a database (e.g. the 45 million vehicleson the Police National Compute。