The story of Charles Cullen, who told investigators he killed up to 40 patients while moving from one nursing job to another, shows what can happen when hiring managers don't share information.

The problem goes well beyond the health care field, though. Businesses in all industries share hospitals' reticence to talk about former workers.

It has become a common human resources policy not to comment on past employees' work records. Companies fear the worker will challenge as untrue a negative reference in court. Those suits can be costly, even if the company wins.

"We're a litigious society," said Michael Boyle, an executive recruiter in the Philadelphia office of staffing consultants Spherion Corp. "We'll sue for anything in this world."

There are ways to get around the silence from human resources, such as calling former supervisors for "informal reference" interviews. Such backdoor interviews are common, but require good connections and trustworthy sources -- and can also be grounds for legal challenge.

In Cullen's case, his former employers' refusal to share information helped him jump from hospital to hospital in the Lehigh Valley and New Jersey. The facilities that hired Cullen said they did not know of suspicious deaths and investigations in his past.

The same thing can happen in the general business world, as the case of Paul Calden shows. Calden shot five former co-workers, killing three, before killing himself in 1993 at a Florida office of Fireman's Fund Insurance Co.

The company had hired Calden in part because of a brief reference letter from his previous employer, insurance giant Allstate. The letter reportedly said Calden was let go as part of a corporate downsizing. He actually was fired for bringing a gun to work and threatening co-workers.

The victims' families later sued Allstate, claiming it knew Calden was dangerous but did not tell his new company. The case was settled in 1995.

Businesses already were cracking down on their references at the time of Calden's rampage, said Craig Pratt, an Oakland, Calif., human resources consultant. The well-publicized case further convinced human resources professionals that less information was better, since a consistent no-comment policy cuts down on liability.

"We had a huge tightening up in the late '80s and early '90s," he said.

By 1998, when a national trade group surveyed 850 human resources officials, the fear of references was no longer a new trend. It was the norm.

The survey, by the Society for Human Resource Management, found an unspecified majority said they only confirmed basic factual information, such as job titles and dates employed.

The survey noted that "details of former employees' personality traits, violent or bizarre behavior, human relations skills and work habits are among those pieces of information most respondents' organizations rarely or never provide when giving references."

The basic facts -- name, start date and end date -- are what Sacred Heart Hospital at Allentown gave out last year, when a New Jersey hospital called for a reference on Cullen. And that's what the Allentown hospital got when it called Cullen's previous employer.

Cullen, of Bethlehem, faces one count each of murder and attempted murder charges in his still developing case and tried to plead guilty to those two charges Monday at his arraignment. He told investigators he killed 30 to 40 people during a 16-year nursing career.

Hospitals and other companies said they give only minimal information because of lawsuit worries. But such suits are rare. Only 1 percent of companies in the human resources survey said they had been sued for defamation or negligent hiring. And companies that land in court can rely on the age-old defense against defamation -- truth.

"If you don't defame somebody, then you are going to be able to say what you want," said attorney Jordan Yeager of Boockvar & Yeager, a Bethlehem law firm specializing in labor and employment law.

But fighting a claim takes time, money and detailed records to back up a company's comments. So, for most companies, saying little or nothing is the most prudent option, labor law experts say.