The murder charges against a Suburban Hospital employee who police say killed his boss over workplace disputes have raised questions about how a man with a violent past slipped through the background checks the hospital says it routinely employs. Suburban spokeswoman Ronna Borenstein-Levy said the hospital conducted a background check on 49-year-old engineer Keith D. Little -- accused of stabbing his supervisor, Roosevelt Brockington Jr., more than 70 times in Suburban's boiler room -- but that check "did not return information on prior arrests and convictions."

But court records show Little was charged with second-degree murder in a 2003 D.C. slaying but was found not guilty in a jury trial. He also served about six years in prison after he was convicted of several assault charges and obstruction of justice related to a 1984 attack.

Borenstein-Levy said police and prosecutors have told the hospital that cases that result in an acquittal or successful appeal often do not appear on background checks.

She would not elaborate on Suburban's procedures for conducting background checks.

The hospital also asks employees to self-disclose past criminal convictions and pending charges, according to its online application. The application says that a criminal record "will not necessarily bar you from employment." It says the hospital considers factors that include the person's age at the time of the conviction, how much time has passed since then, the nature of the offense and rehabilitation.

Conducting background checks and asking self-disclosure questions during hiring are the best ways for employers to avoid bringing potentially violent people into the workplace, said John Mahoney, a labor and employment lawyer with Tully Rinckey.

"They need to do thorough background checks to make sure that the folks that they're hiring are safe," Mahoney said.

Little, of Lanham, was ordered to remain in custody without bond on Friday. A preliminary hearing in the case is scheduled for Feb. 4.

No lawyer was listed for Little in court records.

Brockington's slaying prompted a four-hour lockdown at the hospital on New Year's Day. Brockington had recently given Little a poor performance review, which may have provided the motive for the slaying, police said.

On Wednesday night, another hospital employee saw Little with a bucket that contained a black ski mask and black gloves in chemically treated water. Police say surveillance video shows Little hiding the items in a trash can.