Closed circuit television (CCTV) cameras are commonly implemented to deter crime. Especially used in the United Kingdom, CCTV cameras can be seen on nearly every corner of London and other major cities. Many cameras are needed for monitoring cities, and the number of cameras used has grown tremendously over the years. The majority of CCTV cameras are used for basic security surveillance, normally to prevent theft.
Purpose
There are a couple of purposes behind the implementation of CCTV cameras. One basic idea is that by having cameras everywhere, any crimes that are committed will have video evidence that can be reviewed. With video evidence, crimes are much more likely to be solved.

The other idea behind CCTV is that it will serve as a prevention technique. If everyone knows that they are being recorded, then they should be less likely to commit crimes in the first place to avoid the repercussions.
Introduction
CCTVs were introduced in the 1970s as an analog system. Since then, the majority of cameras have been upgraded to digital, which are easier to manage and don't have to rely on large cable systems for data transmission and recording.
Numbers
CCTV is very popular in many areas throughout the world, mostly as a surveillance technique in small areas. The United Kingdom has implemented them as police surveillance techniques for cities as well. More than 25 million CCTVs are in operation around the world, 2.5 million of which are in the UK.

Statistics show that in major cities like London, the average citizen is caught on CCTV cameras at a rate of almost 300 times per day.
Theft Prevention
One of the main focuses of CCTVs is theft-prevention. The idea is that this serves to deter theft, as well as to ensure a guilty verdict is carried out when a theft occurs. According to Hugh Marriage---a crime reduction officer for the southeast of England, "CCTV pictures means there have been an enormous increase in guilty verdicts." Each guilty verdict saves an estimated 3,000 to 5,000 pounds.
Terrorist Incident
One of the most highly documented success stories of CCTV cameras is the July 2005 bombing in London, where CCTV images helped with the identification of people that played a key role in the attack and ultimately lead to their convictions.