By Mitch Lipka

Jan 2 (Reuters) - If you are mad as hell about a consumer experience you've had, you may want to exercise your right of free speech to express your dismay in a public forum - these days, by posting a negative review on a site like Yelp or Angie's List.

But a lawsuit in Virginia may make you think twice about how exactly to word your gripe to avoid provoking a defamation lawsuit that could cost you, whether you end up guilty of defamation or not. At a time when consumers routinely rely on what other consumers have to say about products and services, the case has bearing on the boundaries of online behavior.

The Virginia dispute started when homeowner Jane Perez posted negative comments about Washington, D.C.-area contractor Christopher Dietz to Yelp and Angie's List in the fall of 2012. Perez's comments accused the contractor of stealing her jewelry and charging her for work that was never done, according to a lawsuit filed by Dietz accusing Perez of defamation.

In early December, the judge in the case, Thomas Fortkort, ruled that portions of the reviews had to be removed from the sites.

That prompted the intervention of lawyers from advocacy groups Public Citizen and the American Civil Liberties Union, who filed an appeal last week that asserted the judge's decision amounted to prior restraint - action that prohibits speech before it takes place and is generally regarded as a violation of First Amendment freedom of speech rights.

The Virginia Supreme Court, in a decision made public Wednesday, overturned Judge Fortkort's injunction, saying it was "not justified."

The defamation case now goes back to Fortkort, who can set a trial in the case. A veteran litigator has agreed to represent Perez for free; she has had to spend her own money to this point, something that made her consider giving up the fight, according to Public Citizen.

"The decision confirms the importance of not shutting down public discussion on the Internet just because someone doesn't like what's being talked about," says Paul Alan Levy, an attorney for Public Citizen.

HOW TO PRACTICE SAFE CRITICISM

When consumers do let fly and provoke a reaction, more often than not they face just the threat of litigation, intended to get them to voluntarily withdraw the reviews, says Eric Goldman, director of the High Tech Law Institute at Santa Clara University Law School in California. Actual litigation is rare.

"Businesses that choose to sue their customers to silence them rather than address their comments rarely prevail and often bring additional unwanted attention to the original criticism," says Yelp public relations manager Kristen Whisenand.

Nevertheless, with consumers writing millions of reviews without lawyers poring over them (Yelp.com alone has more than 30 million user reviews posted to its site), some are taking risks - even big ones, says Goldman. "Most people don't know the legal nuances of how to write negative reviews without making defamatory statements," he says. "Every time people post negative online reviews, they are betting their houses - in the sense that the criticized business can sue them and try to take their house."

Under the law, defamation involves making a false statement that harms someone's reputation. Other factors may come into play, including fault or negligence by the person making the statement. When a statement concerns a public figure there are still more factors.

While Goldman favors a federal law to protect consumer opinions, he suggests staying focused on facts and personal experience to avoid potentially problematic commentary that could end up being called defamatory.

If you're writing about your experience with the plumber, for example, explain what happened: You called because the pipes were clogged or the toilet overflowed. Detail what your experience was like. If you were gratified the plumber took your call right away, say so. If you were frustrated because it took hours to get a call back, say that.

Focus on facts like how long the plumber was there and whether the job was completed, or that it cost $500 for a five-minute visit that only involved the use of a plunger. Mad that he was on your dime while taking an extended lunch? Say what you saw without embellishment, Goldman says. Calling him a crook could have consequences.

Most of all, offer information that can benefit others. "Your goal shouldn't be to punish the vendor; it should be to help your peers make better marketplace choices," says Goldman.

(The author is a Reuters contributor. The opinions expressed are his own.)

Follow us on Twitter @ReutersLegal | Like us on Facebook