No it isn't. People have imperfect memory, and if the police can knowingly lie to you, then they can also convince you to admit something which never happened,

No it isn't. People have imperfect memory, and if the police can knowingly lie to you, then they can also convince you to admit something which never happened, effectively coercing you to fabricate evidence against yourself. Yes, it may lead to some bad guys getting caught who otherwise wouldn't have been. But that is not an excuse if it also compromises the rule of law for innocent people.