"If he has gone all lawyered up and refused to talk to them he would have essentially confirmed everything that they assumed they already knew. They would have arrested him, and only by the actual trial would the truth come out."
Obtaining a lawyer does not in any way imply guilt - you are exercising your right to an attorney and proper process of law. Watch the video.
"If you are innocent cooperate as much as you possibly can - up until you are arrested. Once you are arrested, then, and only then, is it time to get a lawyer. Because if you are arrested then they think you are guilty and cooperating is not going to change their mind."
No. If you are _accused_ you should get a lawyer. A seemingly innocent statement can be completely taken out of context, again watch the video. Also, you are being foolish if you think you can change an officer's mind about arresting you by talking to him. I'll say it again, whether you are guilty or not, the only words out of your mouth when you are accused of a crime should be "I'd like to speak with a lawyer"