This undated photo provided by WDBJ-TV, shows Vester Lee Flanagan II, who killed WDBJ reporter Alison Parker and cameraman Adam Ward in Moneta, Va., Wednesday, Aug. 26, 2015. Flanagan had a history of threatening workplace behavior, former co-workers say. (WDBJ-TV via AP)

Vester Lee Flanagan II, the man who authorities say shot and killed two journalists in Southwest Virginia during a live television broadcast Wednesday, had a history of contentious relationships with his employers and colleagues: He filed at least two lawsuits against former employers alleging racial discrimination and unfair treatment, and another alleging wrongful termination. Former colleagues of his have described a pattern of threatening behavior in the workplace. 

It is unclear how much Flanagan's employers, including WTWC in Tallahassee, Fla., and later at WDBJ in Southwestern Virginia, knew about his track record.

The case puts a spotlight on one of corporate America's trickier tasks: unearthing potentially negative information about a prospective employee before it hires that person. Potential legal issues can make it difficult for hiring managers to put together a complete picture of a job candidate, employment attorneys say.

[‘This gentleman had issues. People needed to know it,” Va. governor says of shooter]

Background checks: The majority of employers have made them a routine part of their vetting process. But background checks are not required for most jobs, and there’s no industry standard for how they should be carried out.

Many employers only look for criminal convictions and even then limit how deeply they poke into the potential employee's background because the tests are expensive to conduct.

“I’ve had cases where we get in a lawsuit and we find that the person had a long criminal record in Maine or something, and the employer is here in Texas and they never ran a criminal background check in Maine,” said David Barron, an employment attorney at international law firm Cozen O'Connor.

Some employers may feel further constrained by the type of information they can weigh in a hiring decision. Considering whether a person has been arrested for a crime is illegal in many states. The Equal Employment Opportunity Commission has also issued guidance saying that it might also break federal law for employers to consider arrests that did not lead to convictions, employment experts say.

An employer background check is also not likely to unearth the kind of civil lawsuits Flanagan filed against his employers, experts said. Plus, it can sometimes open a can of worms: The details of the lawsuit could include personal information, such as the applicant's sexual orientation, which is supposed to be protected information during the hiring process.

“Sometimes it gets you into information you don’t want to know,” said Kevin Simon, a partner at employment law firm Fisher & Phillips.

Reference checks:  Checking someone's references could be valuable for learning about a prospective hire. But past employers often give only the most cursory information when asked about a former employee, providing the person’s title, salary and the dates during which they were employed.

Offering much more information can open the door to legal issues.

Telling a prospective employer about a worker’s rocky tenure could lead to a defamation suit, experts say. If the worker finds out after they were turned down for the job after a negative review, they can blame their former employer and sue. 

Given that Flanagan had filed discrimination lawsuits, that may have created additional considerations for his past employers about what to share with prospective employers, experts said.

“If by chance the employee had filed any sort of discrimination complaint internally, or maybe externally with the EEOC … if the employer who had been complained about then tells a future employer about those charges or complaints, they could also be sued for retaliation,” said Elizabeth Bille, vice president and associate general counsel for the Society for Human Resource Management.

Some states have tried to establish legal protections for employers so that they can’t be held liable in a defamation suit for a reference that did not contain false information and was given in good faith.

“The problem is that a number of employers don’t even want to have to go to court to defend themselves even in the most basic way...they want to avoid the situation altogether,” Bille said.

Interviews:  The interview process is another avenue for probing whether a worker has a troubled employment history. Does a person have a good explanation for why there are two years unaccounted for in his or her work history, for example?

“If they stumble, it may be that they’re trying to hide a previous employment situation that went bad,” Bille said. 

But asking tough questions is, of course, not a sure way of getting to the truth.

“There aren’t a lot of restrictions in terms of what they can ask directly," Simon said. "It’s how do you verify what the applicant tells you that’s the challenge."

Correction: An earlier version of this story incorrectly attributed a quote from Elizabeth Bille to Pamela Devata, a partner in the labor and employment practice group of Seyfarth Shaw who The Washington Post interviewed for this story. The earlier version also included an incorrect spelling of Devata's last name.  This version has been corrected.