Lying in court is common and rarely punished, but that doesn't mean it's a good idea.

One of the things schools don't teach in courses on the court system is that in almost every trial, at least one of the parties will step up to the witness stand, swear to tell the truth "so help me God," and then sit down and violate that oath.

Lying under oath is an accepted element of many trials. If that weren't true, there would be little need for a jury. That's because a necessary part of deciding whose version of disputed facts is true -- for example, was the traffic light green or red when the accident occurred? -- often involves deciding whose story to believe.

Once the jury decides whose story is true, it is the judge who applies the law to these "facts" and ultimately decides what the judgment will say.

Another fact little known to those who don't live in the court system every day is that there is rarely any earthly punishment for lying in court. There is, of course, the crime of perjury. Here is how California defines it (a definition that's pretty typical of those used by other states):

"Every person who, having taken an oath that he or she will testify...truly before any competent tribunal..., willfully...states as true any material matter which he or she knows to be false...is guilty of perjury."

But anyone who has been around the court system for awhile knows that perjury is almost never prosecuted. District Attorneys justify this by saying they have learned juries won't convict anyone of perjury no matter how strong the evidence. Whether this conclusion is based on actual experience or myths passed down from their elders isn't clear. For example, several years ago Judge Roderic Duncan, of the Alameda County Superior Court, sent what he describes as "a slam-dunk case of perjury" to the local D.A. Judge Duncan pointed out in his letter that "one of the parties admitted in my court that he had lied under oath." The D.A. never even responded to his letter.

One peculiarity Judge Duncan has noticed in judging at several levels of the court system is that small claims court seems to be the most perjury-free. He says, "day after day, in case after case, I recall people standing up in small claims court and testifying to facts that clearly damaged their cases. Things such as: 'Well, the light was either yellow or red, but I thought I would have time to get through the intersection on time...besides, that other car was coming on entirely too fast.'"

However, Duncan also says that in Superior Court, "where I sat for many years, it is extremely rare to hear anyone admit something that might damage their case. For example, in Family Court, no one I know has ever heard a wage-earner in a child support case admit that he was earning overtime and therefore really should pay more support."

Duncan goes on to ask whether the fact that witnesses seem more honest in small claims court -- where lawyers aren't allowed -- is attributable to the fact that when a lawyer gets into a case, he or she will advise the client to lie. He responds, "In a few cases I am sure it happens, but in most instances I think a lawyer just points out to the client that if he admits he is still earning overtime, the judge is going to increase the support he is ordered to pay. The client understands that truth equals a financial hit and decides to lie."

Is the lawyer doing something wrong when she explains to a client what type of testimony might result in a victory? Judge Duncan says "It depends on nuances too delicate to quantify. A lawyer who explains the adverse consequences of certain testimony is only doing his or her job. A suggestion that the truth be 'modified,' of course, is unethical behavior."