In court, law enforcement is allowed to testify to whatever they "recall" during conversations with you. And you won't be able to challenge it whatsoever. You are testifying against yourself when you do this, even if you are 1000% innocent - they might "recall" differently. And then you are screwed.
Everything from "do you know how fast you were going" to something much more extreme like this case.
At least that's the bit that convinces me there's no good to be had in talking to law enforcement.
However, the prosecution, meaning the DA and his office, are required to disclose to you and your attorney anything that would support your innocence (known as exculpatory evidence).
I'm not a lawyer, so it's not clear to me how this interacts with the cop's role. As a witness, I guess he wouldn't have to offer anything. But as the guy who arrests you, I'd think that he's part of the "prosecution team", and thus would be covered by the rules of exculpatory evidence. Anybody know more than my supposition?
The gist of it is that he completely agrees with Professor James Duane that talking to the police always goes against your best interests, and goes on to discuss practical interview techniques that the police use to get suspects to talk.