And I think I could summarize it by finishing the sentence he was going for:
"Don't talk to the police... without a lawyer."
First, if you're brought in for interrogation they have already "arrested" you. I.e., put you in handcuffs in the back of the car, no you aren't free to go, that sort of thing. The police officer says he's let a couple of people go who he knew were innocent after their interrogation. You don't describe the circumstances so we'll never know if he found out they were innocent after talking with them and their lawyer, or if they just talked. Even if the person just talked to the cop without a lawyer present and they decided to let him go, that's taking a big chance considering you don't know if you'll get the cop with the heart of gold going into it.
The cop is trained to talk like a good guy because they want to coerce a confession out of criminals. Even with that in mind, there are times when things don't add up in the cop mind and they decide the person is guilty. I've been in a couple of real far-fetched situations and tried to explain to the cop what was happening (things like, my mom buying a car one day so I'm driving a car with no tags. She hasn't yet signed the title. I'm in a state where she bought the car, she lives in a different state and I live in a third state. She bought it used from someone out of a parking lot so I'm trying to explain all this while praying the guy didn't just steal the car and sell it to my mom..)
So yeah, luckily they didn't take me down to the station. They didn't handcuff me. If they had handcuffed me I would've stopped talking then and asked for a lawyer because having watched the video I know, from what the cop even said, you aren't talking your way out of handcuffs. They are taking you to jail.
As far as evidence entered into the courtroom, I think you'll find that each side is allowed to present evidence however they see fit and the cops/DA will spin it towards you being guilty. That's IF your case goes to trial because the DA is going to lean hard on you to take a plea bargain (saves money for them).
Here's the situation (happened to my friend):
My friend and a buddy are hanging out after going to the shooting range together. Later that night drunken argument of some kind happens, guy pulls friends gun on him (unloaded apparently) and guy leaves the apartment with my friends gun. He throws that gun in the bushes. My friend locks up the buddies gun and figures the dude will sober up and come by the next day to get his gun.
Buddy calls the cops. They show up at 3:00am, arrest friend, confiscate gun. They don't believe the story (I'm not even sure I believe the story but whatever.. it's a story)
The buddy told the cop that my friend pointed the buddies gun at him, so he grabbed the other gun and fled. At the grand jury, the buddy decides the story isn't suspicious enough so he alters his testimony to say the friend broke into his car.
That right there should be a lawyer's paradise. They should have had enough evidence to show the buddy is an unreliable witness and dismiss the whole thing, but the DA goes to my friend who's still in jail and says this: It's your first felony, we'll get you probation only if you plea bargain now (oh, plus fines and this all being on his record and things..) the caveat being if he fights it then the plea goes away and they'll push for 5-20 years in prison. Additionally he doesn't qualify for appointed representation because his salary (which was lost due to him being in jail) is too high.
So what would you do in that situation? Go to prison on principal because you're innocent and your buddy is a poor liar, but somehow they made the case stick? Do you take that chance or accept the plea bargain?
I really suggest you retain a lawyer or pursue law if you think you're onto something new and exciting. The truth of the matter is that the 5th amendment is there to protect anyone who may be innocent and you can't know what circumstances they would need to use those rights without careful study of the law (lawyers can research and find example cases for you for a fee if you wish)