Yes and no: There are currently no laws criminalizing the act of secretly recording a public official. The recording may also be used as evidence in proceedings against that officer. However, a person who secretly records another could be in violation of that person's right to privacy guaranteed by the constitution and could be sued.
The acceptance of recordings as evidence will be evaluated case by case.
You are not allowed to film a public official as they are going about their duties as private citizens.
It is forbidden to film in areas where "no photography" or "no filming" signs are displayed. This is often seen at places like military zones and at airports.