The "first thing" is not necessarily Miranda rights. It's not even required to be the "first thing". Miranda is required once in custody and prior to interrogation. In a cop car and "just talking"? Well...'Your honor, I wasn't interrogating Mr Johnson, I just noticed he seemed upset and asked him how he was doing and why he was crying, then he just told me this stuff'.
Just because something is in every movie and TV show has them doesn't mean that's how the real world works. Moreover, that probably doesn't do anyone a service, if I've watched cops read the Miranda rights to folks on TV, and they haven't said them to me, maybe I could assume that I'm not being interrogated yet. Or maybe I could assume that since they haven't been said that nothing I say is admissible in court and can mouth off. Who knows? The point being, the Miranda rights aren't some magic set of words that can iron-clad make things better or worse.
Also, I'm not sure why you find one lie (your buddy confessed) ok but another (we have fingerprints) is not. Lying is either OK, or it's not. As soon as you start deciding which lies are ok and which aren't, I think you're firmly on the slippery slope.