Earlier this month, Charles Cullen, the nurse who pleaded guilty to killing at least 29 patients in hospitals in New Jersey and Pennsylvania, was sentenced to 11 consecutive life terms. He is no longer a danger to society, but the underlying problem that allowed him to kill still is.

During his 16-year nursing career, Cullen was able to move from one hospital to another – to 10 medical facilities in all – because fear of litigation prevented those hospitals from giving him a bad reference. Co-workers observed his strange behavior, and caught him in rooms of patients with medications that weren’t appropriate. But they didn’t know he was murdering people, and couldn’t prove that he was doing something illegal. So the hospitals would eventually let him go, and, when the next hospital in line asked for a reference, merely gave the stock response of all employers nowadays: “We confirm that he worked here from this to that date.”

Even the Pennsylvania Department of State, which oversees the state nursing board and had been warned about Cullen’s penchant for diverting medications, could not comment on his reputation. “Legally, we can’t speak about any information we receive that doesn’t result in disciplinary action,” a spokesman said.

“What I’m coming to understand,” said Dr. William Cors, the chief medical officer of Somerset Medical Center in Somerville, N.J., where Cullen last worked, “is that, short of an actual conviction or revocation of license, none of this information gets shared. If anything good comes from this, it would be to reform the system where we’re prevented from telling one another what we know out of fear, quite frankly, of being sued.”

America’s lawsuit culture has bred all kinds of bizarre changes to our society – warning labels on coffee cups, and doctors squandering billions in defensive medicine, to name just two. But the inability to be honest about how you feel about other people is one of the most destructive. Making judgments about people is the currency of a social interaction in a free society. Who tries hard? Who has good judgment? Who is a pleasure to deal with? And who acts in a way that makes your skin crawl?

We’re told we live in a free society – where the First Amendment supposedly guarantees freedom of speech – but somehow we no longer can express our opinions about other people. This change is the outgrowth of our guilt about racism and other forms of discrimination. But there’s a difference between guarding against patterns and practices of discrimination – which generally affect a category of people – and making judgments about a particular person.

Lawsuits – more precisely, the unilateral availability of lawsuits – have an in terrorem effect that freezes free speech. Legal process is too expensive. Moreover, judgments about people, as with Nurse Cullen, are rarely susceptible to “proof” – How do you prove someone has bad judgment, or doesn’t try hard, or acts too strangely? Better to avoid litigation by not giving references at all.

Employment lawsuits, often driven by injured pride, have flooded federal courts and are notoriously unreliable. The assumption seems to be that people will only sue if the claim has merit. But that’s not accurate. The more incompetent a person, studies have shown, the less likely the person will realize his own incompetence. A federal judge described to me a case where, after a trial that demonstrated overwhelmingly that the claimant was not up to the job, the plaintiff wept with frustration at the injustice.

Clearly this has gone too far. In the wake of these murders, New Jersey passed a law requiring hospitals to share information about employees. But next time the psychopath will be in a school or business.

Employment law must be changed to promote honest opinion on matters of character and competence in all areas of society. Many states offer “qualified immunity” for job references, but the loopholes are easy to find (for example, just allege “bad faith”).The only effective answer is to create a foolproof immunity for employee references – no claim will be entertained unless the judge determines at the outset that a high hurdle of intentional misstatement has been met. More broadly, there should be a re-examination of employee litigation, and perhaps substitute a complaint bureau or summary arbitration process for most individual claims.

Our modern sensibility is to worry about the unfairness of a mean-spirited supervisor trying to sabotage someone’s career. But our fear of occasional unfairness has now led to a tidal wave of unfairness, where good people aren’t honored and bad people get away with murder.

Mr. Howard, a lawyer and author, is chairman of Common Good, a bipartisan coalition to restore reliability to American law (www.cgood.org).