How can you protect yourself during interrogation?
In your witness statement, you are legally entitled to keep silent. You don't have to admit it even if you are guilty. You may tell police that you reserve the right to explain yourself in court.
If you cooperate, it will help police to investigate further. For example, if you are innocent and arrested with drugs in your car, you can say it is not yours and they belong to someone else.
Police may accept your explanation and look for the other person. If you don't cooperate, police will say you must be the only person.
Torture or coercion to force your confession is not allowed albeit some documented cases of such instances.