Elizabeth Cromwell sued the province earlier this month, alleging a lack of control over the potentially deadly drug led to the death of Clayton Cromwell on April 7, 2014.
The prison provides methadone to some prisoners as part of a medical program, but the 23-year-old didn't have a prescription and it remains unclear how he obtained it.
A Crown lawyer says in a statement of defence filed Friday that Central Nova Scotia Correctional Facility personnel didn't know that Cromwell had the drug and followed proper procedures to ensure he didn't have access to it.
The statement, which has not been proven in court, says Cromwell broke prison rules by having the drug and voluntarily took the drug "when it was unsafe to do so."
"The defendant pleads ... injury, loss or damage was caused by Clayton Cromwell's own actions and was not caused by a breach of any duty owed to Clayton Cromwell," says the statement, signed by Crown lawyer Duane Eddy.
Cromwell was awaiting a court appearance for allegedly violating probation in a drug trafficking case.
The family's lawyer, Devin Maxwell, has said an internal report into the death completed last July concluded that an intercom system that allowed inmates in one of the unit's cells to call for help wasn't working.
The statement of defence admits the intercom in the West Unit cell wasn't working, but denies this amounted to negligence or caused Cromwell's death.
Maxwell has also said the report states that another inmate overdosed on methadone the day before Cromwell died.
The lawyer has said the report states the men were locked in their cells, but it doesn't indicate if a search was carried out.
The statement of claim doesn't address the issue of whether a search was carried out.