The question is not whether your client did the act for which he is being prosecuted by the State, but whether the prosecution can prove it. Many defense attorneys don't ask themselves this question. Contrary to the lay and expert commentary alike, the criminal jury trial is not for the purpose of finding the truth; the purpose of a criminal jury trial is to establish proof that the defendant did the act for which he is charged. The common cry is the failure of the jury system if the person who did it, is found not guilty. This is not a sign of failure but of success--the government must prove he did it and if they can't do that, too bad for them.
One effective method of analyzing the probability that a defendant will be convicted if he goes to trial is the strength of the prosecution's witnesses. The prosecution must often rely on very unreliable people to prove your client's guilt. There are several uncertainties involved: Did the potential witnesses tell the cops the truth when giving the initial report? Will the witnesses even show up for trial?
Will the prosecutor be able to find the witnesses to subpoena them? Will the witnesses be believable if they do testify? Many a case has been dismissed because the answer to one or more of these questions has been no.
I am aware of defense attorneys with the view that if the defendant did what he is charged with, he should plead guilty to it or at least to a lesser included offense. Apparently we are all required to accept responsibility for our acts whether this acceptance will land us in jail or not, whether we will be required to pay a significant fortune in fines, costs, and attorney fees before we will be able to drive a car again legally. This is not representing your client; this is not the function of a criminal defense attorney. Our law schools teach how to try a case to a jury; but they don't inculcate in their students the idea that they should actually try a case now and again.