For a private investigator, each case is different, so there’s a need to use a variety of techniques and tools in order to obtain data.   Here are the different types of surveillance followed by most private investigators:   ●     Physical surveillance – The most commonly used tactic by most detectives. It involves following and observing the subject from a certain distance using a disguise to avoid looking suspicious. ●     Technical surveillance – This is used to gather evidence that can be played back and reviewed later on. It usually involves recording devices such as movement sensors, hidden cameras, microphones, and video recorders. ●     Digital surveillance – It involves tracking the behaviour of the subject online, may be done either in an intrusive or non-intrusive way. Some detectives follow their social media or use online search, but others go as far as hacking their accounts.