McCarthy Hall, a dormitory where a student made ricin, is photographed on the Georgetown University campus earlier this year. (Katherine Frey/The Washington Post)

A Georgetown University student who was arrested for manufacturing the deadly chemical ricin in his dormitory room in March, was sentenced Monday in U.S. District Court to a year and a day in prison.

In issuing her sentence, Judge Ketanji B. Jackson said Daniel H. Milzman’s intentions for manufacturing the chemical were “ambiguous at best” but that Milzman put numerous people, including his classmates and dormitory roommate, at great risk.

Jackson also ordered Milzman, 20, to undergo a mental health evaluation, serve two years of supervised probation and perform 400 hours of community service. Milzman has been in an isolation cell in D.C. jail since his arrest. Attorneys say Milzman could be moved to a halfway house in January because of the 71 / 2 months of jail time he has served already, which is being credited to his sentence.

Milzman pleaded guilty in September to unregistered possession of a biological agent or toxin. Before he was sentenced, Milzman, dressed in an orange Department of Corrections jumpsuit, apologized as 70 friends and family members, including his parents, looked on.

“I never intended to put anyone in any risk of danger. My actions were reckless and unacceptable,” he said. The Bethesda native apologized to his family, friends and the university. “I am sorry I broke the trust you placed in me,” he said.

Milzman’s attorneys said he had no plans to harm anyone other than himself when he met with a classmate and student resident adviser on March 17 and, according to court charging documents, pulled out a double-wrapped plastic bag and tossed it on the floor, telling his friend that the bag contained ricin, which he had manufactured in his dorm room while on school break. The adviser alerted authorities.

Milzman attorney Danny Onorato told the judge his client had planned to use the deadly poison to commit suicide as a result of years of mental and emotional problems that were diagnosed when Milzman was 10.

“He was depressed and suicidal,” Onorato said. He added that Milzman, a science major who had planned to become a medical doctor, did not want to kill himself in a way that would cause emotional distress to his parents and family, such as by hanging. Milzman, Onorato said, instead researched how to make ricin.

But prosecutors Maia L. Miller and Frederick W. Yette characterized Milzman as having had a calculated plan and asked the judge for a two-year sentence. Miller said Milzman searched for a “recipe” for ricin on the Internet, used protective gloves and eyewear while he was mixing the chemicals in his room and waited until his roommate was out of town to start working on the deadly poison. Miller said authorities think Milzman developed the idea to use ricin to kill after watching an episode of the TV crime drama “Breaking Bad.”

Miller also said the resident adviser told authorities that Milzman had denied that he was going to use the toxin on himself in a suicide attempt. But when the adviser asked Milzman if he was going to use it on someone else, Milzman “shrugged” his shoulders, Miller said. “This was deliberately thought out and well planned,” Miller said.

Miller also quoted from a Facebook message Milzman allegedly e-mailed to a friend during a dispute in which Milzman told the friend he was “useless” and that the only use for him would be if he were “chemically disincorporated” and his “parts were sold.”

In issuing her sentence, Jackson said she believed Milzman was remorseful but said she was not convinced he had planned to use the toxin on himself. “His intentions are ambiguous at best,” she said.

After the sentencing, Milzman's father, David Milzman, stood in the hallway hugging dozens of family members and friends. Many of them declined to comment. But the senior Milzman said he wanted to thank his family and friends “for their support.”