It depends on what you are lying about. Police officers using their position to intimidate legally illiterate suspects into confessions by threatening them with severe punishments or coaxing them with the possibility of extremely easy treatment is at least to me a type of deception that egregiously taints the accuracy of what is confessed and should not be used. This is different from an officer saying "We have X evidence, you are going to go down its only a matter of how cooperative you want to be." or "Your partner Y confessed, are you going to take this alone?" While also potentially coercive I think they are more acceptable.