There are times when a policeman has to lie to a suspect to get the information necessary to provide justice, but some lies are just inexcusable. A policeman should never lie to a citizen about their rights. Such an action should be made illegal, since it causes citizens to fear their local law enforcement.
A person's most fundamental right is to information about their rights.
For example, when a policeman asks to search someone's car without just cause, and the person asks, "Can you make me let you into my car?", the policeman should not be allowed to lie and say "yes."