Surveillance is the word of complete spy on the suspect to gather the evidence and clue of the investigation. Investigators say, surveillances is the backbone of investigation and the key to getting the ride on suspect/ suspects.
There are two types of surveillance
In the electronic surveillance, enforcement agencies depute teams on the suspect to get information of his/ her mobile calls, social media interception, messengers information etc. If the suspect found guilty for the crime. The agency informs to judicial authority with evidence proof.
Electronic is a highly sensitive matter in India and only authorized to get details/ information a Govt. enforcement agency.
Physical is the most common services in the private and Government investigation agencies.
In the physical, a person follows to suspect by the vehicle (bike or car) or by walking. A investigator should have good knowledge how to do investigation in the field. This is the basic requirement for investigators. but sometimes new investigator does mistake while the following suspect to the lake of knowledge. This could be very critical for those agencies Govt. or private if the investigator caught by subject.
There is no change to leave without the compromise with the subject. But an experience in investigation goes succeed from this possible because of experience and save the importance of the case.