Physical surveillance is monitoring a target's location and activities via direct lines of sight instead of by electronic means. Law enforcement agencies use this method of surveillance extensively as a secure and legal way to collect evidence. Unlike electronic surveillance, physical surveillance does not require warrants to execute. Because it's difficult to identify a physical surveillance operative, the technique can be used to track even the most cautious targets.
Front and Follow
This risky tactic, conducted at close quarters, is used to track targets on the move, usually on foot. Two surveillance operatives approach the target at different times. The first falls in behind the target and begins following him discreetly. The second operative predicts the target's path and takes up a position ahead of him. The two agents continue in this manner until the front operative feels the need to lie low or misinterprets the target's destination. Then the following operative repositions to the front and the other operative falls in behind.
This technique uses three operatives to track a target in close proximity. With A and B in the front and follow positions, C takes up a position across the street. This allows C to provide the target's perceived destination to A, who can then alter her path to maintain a front position. If the target turns a corner suddenly, A can keep walking and take up the C position while the operative who used to be C regroups with B into a new front and follow. Because the three operatives cycle through each position, the target is less likely to recognise any face and realise she is being followed.
This strategy is used to watch targets with predictable routines. One operative monitors the subject during one stage of his daily routine. After a while, the operative breaks off and another operative monitors the next part of the target's routine. Eventually the target's entire routine is mapped out without the risk of revealing, or "burning," an operative who stays on the target for too long. Surveillance operatives can be on foot, in a car or pretending to work in the target's vicinity.
Overwatch, commonly used in cities, is one of the safest surveillance techniques. One operative takes a position on a rooftop or in a high-rise building to watch the target from above. Because the operative can monitor the target for extended periods of time with an extremely low risk of being spotted, other operatives on the ground can avoid being burnt by staying a block or two away from the target. If the target moves out of sight of the overwatch, an operative on the ground relocates to a new overwatch while another operative obtains a temporary direct line of sight on the target. Meanwhile, the former overwatch rejoins the ground team.