No, it's not. They shouldn't be allowed to lie at all
This. If they will lie when they are trying to get you to confess, even if you didn't and couldn't have done it, then why wouldn't they lie to you while they have a gun pointed at your backside as you're on the ground? Why wouldn't they lie on their reports? Why wouldn't they keep up that lie in court and the news? They'll obviously not say "I lied about some detail then they confessed" in their reports. And that omission is itself a lie. Their entire job is lying so expecting them to tell the truth is the exception, not the norm.
You're so anti-cop it's hilarious. ---
The mind is its own place, and in itself Can make a heav'n of hell, a hell of heav'n.