The Rikers Island guard who investigators say left her post without permission while a mentally-ill inmate died in an overheated cell was disciplined before for doing the same thing.
Documents obtained by the Associated Press show that in 2010, Carol Lackner was accused of leaving her post while working in another section of the jail.
Her attorney says she was on break.
Most recently, Lackner was suspended 30 days after the death of 56-year-old Jerome Murdough.
An investigation found she left her post in a mental health observation unit 20 minutes before Murdough was discovered unresponsive.
City officials say he had been left alone in an overheated cell for more than four hours.
The Department of Correction declined to comment, saying personnel records are confidential.
Meanwhile, Murdough's mother is planning a $25 million lawsuit against the city.