I err on the side of silence
When I was young and stupid, and horny, one night my buddies and I decided to go out clubbing in downtown Houston. I had crashed and burned on a date, who probably would have had sex with me, but I didn't put on the moves fast enough. So after drinking half a bottle of wine and a few beers with my buddies I stupidly agreed to drive us to this dance club where we had all picked up girls in the past.
Got pulled over going through a "yellow/red/magenta" light and the interrogation commenced. Needless to say I got arrested and sent down to jail for the night. But, while I was there I refused to answer questions on the video camera (although I did do the sobriety test on camera). Also submitted to the breathalyzer exam.
After making bail -- you know who your real friends are when you need $700 in a pinch as a young twentysomething -- I got an attorney and he gave me the scoop, at least in _this_ situation. He admonished me for ever submitting to the sobriety tests on the road, or for answering questions about how much/when/where I'd been drinking (every time I answered one, that just led to even more questions, and eventually the cop is just trying to get you to pony up the answer he wants to hear). Basically he said cops have the authority to arrest you under some pretty low levels of evidence, because ultimately they can just release you without charges if it turns out there isn't anything to pin you on. His advice to me was for future reference, if I have been drinking and get pulled over, if the cop asks me to get out and perform the sobriety test he's already made up his mind to arrest me. So refuse the sobriety test, refuse the breathalyzer test, refuse to make any statements, until they get you down to the station and on camera your statement is "I am not intoxicated."
It also helps that I don't drink anymore either!
But I guess the moral of the story to me was, law enforcement have pressure to exert, will exert such pressure and playing their game by their rules is stupid and usually not helpful.
Justice is kind of a filler word in the court system, I do agree with the poster who said that the courts care about expediency. That is the truth. A criminal judge's court docket is hundreds a day, and they'd love to see 60% of them plea bargained. You have every right to go to trial, which is the route I took and my case was dismissed on the trial date. The prosecutor was furious and I was relieved out of my mind.