The Vermont state employees' union on Wednesday accused a Corrections Department official of receiving preferential treatment in avoiding charges for allowing an inmate to dispose of heroin she had smuggled into the state prison in Windsor.

The offices of the attorney general and the Windsor County state's attorney said Tuesday that no criminal charges would be filed against Corrections Facilities Executive Robert Kupec or the inmate because there was not enough evidence to prove the case.

"We've heard from many Corrections staff members about this case, and they can't believe that the Department of Corrections and the AG are letting Mr. Kupec's egregious error in judgment simply slide," VSEA Executive Director Anne M. Noonan said in a prepared statement. "Clearly, if it were a correctional officer who had allowed an inmate to flush criminal evidence -- particularly 160 bags of heroin -- they would be put out on leave during any investigation. In fact, if they had such a 'judgment lapse,' they would likely have been fired."

The case involved a woman who was arrested on a parole violation and was suspected of concealing a large amount of heroin in a body cavity. Kupec proposed to the prison superintendent that the woman be offered immunity if she removed drugs and flushed them down the toilet, which she did, prosecutors said.

Prosecutors said Kupec and the superintendent never contacted police about the possibility of drugs or plans to destroy them and did not have authority to promise immunity. Corrections Commissioner Robert Hofmann has said Kupec was motivated by concerns for the safety of the inmate.