"There's two types of cops in the world --Those who've been caught in their lies and those who have yet to be caught."
What you said applies to every person, not just cops. Cops are people also, and are subject to the same failings and weaknesses as private citizens. This a fact NO ONE can deny.
In the course of performing my duty on any given night, I probably get lied to 100 or more by private citizens who have no idea how they came to be in possession of the marijuana I caught them smoking in their car, because heaven knows it is not their's, they are only holding it for a friend.
Yup. The difference is that your lies send people to jail.