Rules of Evidence
Courts are not concerned with "truth," so much as they are concerned with following the rules of evidence. These rules serve primarily to keep out evidence. Lawyers work hard to keep out evidence that harms their clients, and to get evidence admitted that helps them. What is left at the end of a trial is a collection of evidence, a patchwork that looks only vaguely like the world outside the courtroom. To make matters worse, according to one retired federal judge, even after all the evidence is presented, judges simply don't know which facts are true and which are not.
Lawyers get used to this. It's a form of dishonesty if you speak in strict terms, this fighting over evidence, and yet you get used to it. I can't recall how many times I've explained this to a client preparing to testify. It's one of the reasons lawyers sometimes get a bad reputation. They learn to deal with evidence and not, strictly speaking, with truth. This is not merely a matter of semantics. There are so many ways to present the same set of facts that the notion that there is an objective "truth" starts to disintegrate whenever you look closely at it. Scientists in the hard sciences are especially hard-headed about the truth. They are the hardest to convince that the truth per se is not all there is to a legal trial.
An illustration: A civil engineer is injured when another driver runs a red light and crashes into him. The other driver is clearly at fault. The engineer hires a lawyer, who sues for damages, including, among other things, medical expenses, lost income, pain and suffering. The engineer's shoulder is shattered. One doctor compared the injury to a porcelain vase shattering. It will never fully recover. But the engineer is tough, both mentally and physically. He refuses the prescription pain medication; pushes through the rehab in record time; misses only a few days' work. And at trial he is more committed to the truth than he is to winning his case. When asked about his physical therapy, he stands up from the witness chair and starts making a very animated motion as if he is starting a lawnmower. And even though he now has a very limited range of motion, for a moment he looks like nothing is really wrong with him. When asked about his pain, he tells the jury that it's nothing he can't handle. And this is the truth. The other lawyer highlights the fact that the engineer did not take pain pills, that he missed only a few days' work, and that he is able to stand up in a courtroom and look so vigorous. For the engineer, this is honesty: He refused to be defeated, even by a very serious injury. For the jury, it is proof that his injuries were not nearly as severe as his lawyers were claiming.