A former prison doctor pleaded guilty Monday to sexually molesting inmates when they sought medical treatment at the U.S. Penitentiary in Atlanta.

Lewis Jackson admitted to abusing three inmates during October 2011. The 36-year-old physician tried to perform oral sex on the three inmates during the course of their medical exams and tried to engage in anal sex with one of them, federal prosecutors said.

“The inmates Dr. Jackson saw at the U.S. Penitentiary had a right to humane treatment during their incarceration,” U.S. Attorney Sally Yates said in a statement. “Instead, Dr. Jackson used his authority to sexually abuse prisoners.”

Jackson worked as a physician at the sprawling penitentiary, which houses both a minimum-security camp and a medium-security prison, from January 2011 through July 2012.

He faces a separate charge, which is still pending, in Washington for allegedly molesting an inmate at the District of Columbia jail in 2008. Before working in Atlanta, Jackson was a doctor at the Veterans Affairs hospital in Washington.

Jackson was initially scheduled to enter his guilty plea on Aug. 23, but that was delayed because he tried to commit suicide the previous day. He was then hospitalized for seven days.

U.S. District Judge Amy Totenberg expressed concern as to whether Jackson, a little more than a month after the incident, could make a voluntary and intelligent decision to plead guilty. “I want to make sure you are prepared to proceed today,” she said.

Jackson, a native of College Park who was accompanied by his wife and parents to the hearing, indicated he was.

During his hospitalization, Jackson said, he was diagnosed with mental health conditions he was unaware he had. Jackson told Totenberg he is now taking medication, receiving excellent therapy and “I’ve got the most wonderful and supportive family.”

Totenberg conditionally accepted Jackson’s plea out of concern for his mental health and what could happen to him once he is admitted into the federal prison system. She set his sentencing for Feb. 7.

Totenberg said she would formally accept his plea once she learns more about what will happen with Jackson once he receives what could be a lengthy federal prison sentence. Such defendants can become targets of predatory inmates or be housed in isolation, the judge said.

“I’m very concerned about the mental health, the security issues, the segregation issues in this case,” Totenberg said.

Assistant U.S. Attorney Kurt Erskine said the U.S. Bureau of Prisons will have the final word on Jackson’s treatment and placement, but he told Totenberg he would learn more about it before the sentencing hearing.

Both Erskine and Totenberg said they were concerned for Jackson, who is now free on bond.

“We don’t want him to hurt himself like he did in October,” Totenberg said, exhorting Jackson to “stay within the hold of your family.”