You are both right, but if you do that practice and it can be established you did not do it in good faith, your statement will be suppressed. Anyone who cannot see the abuse in this, is turning a blind eye. If you have the pc to arrest someone, but you then hold off on the arrest until you get a non-custodial confession, there could be some questions as to why you waited to make your arrest. If you are not making sense, you could have some suppression issues.