Let’s talk about perjury — a person taking an oath to tell the truth and then lying through their teeth. Perjury is illegal, and one can be both fined and thrown in jail for it.

I don’t know about you, but my parents instilled in me a sense of honesty that makes me get the shakes at the mere thought of telling a lie after taking a sworn oath. I don’t think I could do it. I would be like that person on Law & Order who suddenly blurts out, “OK, I told my boyfriend I’d like to see him dead! I’m sorry!” when I really had nothing to do with the murder in question.

I recently witnessed what I believed to be an act of perjury while covering the Casey Anthony murder case in Florida. The lie will go unpunished, and that bothers me because it’s the justice system saying, in effect, “OK, never mind, that oath you took really doesn’t matter.”

Here’s what I saw happen: Anthony was accused of knocking out her 2-year-old child with chloroform and causing her death by binding her airways with duct tape. She was also suspected of being the one who had conducted more than 80 searches for “chloroform” and “how to make chloroform at home” on the family computer in March 2008.

Her mother, Cindy, stunned court-watchers last month when testifying that she was the one who had been at the home computer on the dates in question searching for chloroform. She explained she had originally typed in “chlorophyll,” and the computer had automatically taken her to “chloroform.” Her story revolved around wanting to know if the illness of their dog was being caused by him eating too many chlorophyll-filled bamboo leaves in the backyard.

The prosecution called computer experts who testified they found absolutely no “chlorophyll” searches on the family hard drive. An executive from Gentiva, where Cindy Anthony worked, testified that her password-protected work computer showed she was actually logged in there on the dates in question. Her work terminal was active all day and reflected the workload she always performed.

In other words, it appeared her motherly instinct kicked in and she lied, thinking it would somehow help her daughter dodge the charge of premeditated murder, which carried the death penalty.

I know after the whole hoopla about Casey Anthony’s murder acquittal it might seem like a small point, but I was upset to hear the State of Florida has decided not to pursue perjury charges against Cindy Anthony. I understand she’s been through a lot, losing her granddaughter and all, but the system cannot allow lies to be told in courts of law with no penalty. It matters because it goes to undermine our whole system.

It’s bad enough when someone gets away with perjury in a court. It may be even worse when someone lies to Congress after swearing to tell the truth. I’m talking, of course, about the case against former baseball great and suspected liar Roger Clemens.

In February 2008, Clemens was called to Capitol Hill to appear before a House committee looking into doping by professional athletes. Lawmakers had before them a long-anticipated report about the problem written by well-respected former Sen. George Mitchell, D-Maine.

Clemens’ name was mentioned in the report 82 times tying him to use of both steroids and human growth hormones. Under oath, Clemens’ longtime trainer, Brian McNamee, had said he injected Clemens with performance-enhancing drugs as early as 1998, when he played for the Toronto Blue Jays. In addition, the pitcher’s good friend, New York Yankee Andy Pettitte, swore he had spoken with Clemens about his use of illegal drugs. He went home and told his wife all about the conversations.

So, what did Clemens say when he testified to Congress? “I’m not saying Sen. Mitchell’s report is entirely wrong. I am saying that McNamee’s statements are wrong. Let me be clear. I have never taken steroids or HGH.” And, he said, Pettitte had “misremembered” their talks. The upshot was that Clemens was charged with six felony counts of lying to the federal government and obstruction of Congress.

Unlike Cindy Anthony, who apparently lied to try to save a daughter from a lethal injection, the perjury allegations against Clemens go to an entire industry — to Major League Baseball, the American pastime. Baseball has taken great strides to try to clean up its image the past few years, and I applaud that. Now, it’s the justice system’s turn.

Federal prosecutors bungled the Clemens trial earlier this month by showing a videotape to the jury that included mention of Laura Pettitte’s comments about Clemens’ doping confession. The judge had ruled that was hearsay and could not be mentioned. After it was, a mistrial was declared, and now there’s real doubt about whether prosecutors will press forward or drop the charges.

I say in the name of justice — another American pastime — there must be a second trial for Clemens. Perjury should never go unpunished.

Diane Dimond is the author of Cirque Du Salahi: Be Careful Who You Trust. Click here for more information. She can be contacted at diane@dianedimond.net.