You can sometimes tell if undercover cops are following you if you notice unusual vehicle presence, strange phone interference or persistent observation.
If you notice someone is constantly following you and watching you or the same vehicle is hanging around you alot or near your home or you notice that same vehicle is always behind you or anywhere else you are then it could be an undercover cop following you.
However in some cases it could be someone else just watching you and could be a bad person as well.
It can be hard to detect if undercover cops are following you as they are trained to blend in and avoid detection.
Someone that seems to be watching you more intently than others and focusing on your behavior, body language and interactions or if someone is deliberately staying on the sidelines and avoiding certain activities or not participating in conversations to avoid drawing attention could be an undercover cop watching and following you or could be an undercover detective.
Another sign that an undercover cop could be following and watching you is that you see the same person in different locations, repeatedly and at different times which can suggest they may be following you.
Undercover police cars also often use common vehicle models in neutral colors like white, gray or black and may have some additional antennas.
If you notice unfamiliar vehicles that are parked near your home, work or regular hangout spots for extended periods they could be potentially equipped with some surveillance equipment and could be an undercover police officer watching you.