A former doctor at the District of Columbia jail has pleaded guilty to sexually assaulting a male inmate who went to see him for medical help.

Dr. Lewis Jackson, 36, faces a maximum of 20 years in prison, prosecutors said. Jackson's guilty plea in D.C. Superior Court on Tuesday came three months after the physician pleaded guilty in federal court in Atlanta to sexually assaulting three inmates there.

According to D.C. prosecutors, an inmate went to the D.C. jail infirmary in November 2008 for an examination of his penis, which had developed a medical condition.

Jackson told the man to remove his clothing below the waist and then, without warning, the doctor tried to perform oral sex on the inmate. The man pushed Jackson away, saying, "Whoa, doc."

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He then grabbed his clothes and fled the emergency room and immediately reported the matter to jail authorities.

The government secured Jackson's indictment last year through the use of DNA evidence.

A D.C. Department of Corrections spokeswoman said Jackson was employed with Unity Health Care, the department's medical contractor, from 2007 through 2009. He worked at the jail on a part-time basis.

Within weeks of Jackson's indictment in the District, he was indicted for similar crimes in federal court in Atlanta.

In November, Jackson pleaded in federal court to sexually assaulting three inmates at the United States Penitentiary in Atlanta.

Jackson, who worked at the federal penitentiary from January 2011 through July 2012, admitted that he sexually abused the three inmates in October 2011.

In each case, Jackson tried to perform oral sex on the inmates during the course of their medical exams. In one case, Jackson also attempted to engage in anal sex with an inmate.

When confronted by special agents, Jackson denied the accusations. After the agents played an undercover recording made by one of the inmates, Jackson admitted he to trying to perform sex acts on the inmates.

He is set to be sentenced in Atlanta on Feb. 7. The most serious charges relating to the sexual abuse of the prisoners carries a maximum sentence of 15 years in prison, prosecutors said.

His sentencing in D.C. will be scheduled after the sentencing in Georgia.

smccabe@washingtonexaminer.com