COLFAX, Wash. -

A former Washington State University doctoral candidate has pleaded guilty to trying to poison his sleeping wife with nitrogen gas.

Whitman County Superior Court Judge David Frazier on Tuesday sentenced 32-year-old chemistry student Jacob P. Forster to almost 70 months in prison for attempted assault.

The Lewiston Tribune reports Whitman County prosecutors agreed to reduce the charges from attempted murder.

Forster's attorney contended his client used nitrogen gas to ensure his wife was sleeping soundly so that she could not stop him from committing suicide with the toxic gas himself.

Cheryl Williams told police she awoke to find a cardboard box covering her head. Prosecutors say Forster then grabbed the box and equipment he'd used to pump the colorless, odorless gas into it and left.