St. JOHNSBURY, Vt. — A snowplow driver and his wife who are accused of killing a popular teacher and dumping her naked body in the Connecticut River in March faced new charges of premeditated murder today.

Allen Prue pleaded not guilty to first-degree murder in the killing of Melissa Jenkins, of St. Johnsbury. Patricia Prue pleaded not guilty to a charge of aggravated murder, accusing her of killing Jenkins during a sexual assault or attempted sexual assault.

A police affidavit says the Prues, who had been charged with second-degree murder and have been jailed without bail, planned to kill the 33-year-old single mother, buying a stun gun and prepaid cellphone and driving by her home and the dam in Barnet where they later dumped her body. It says the Waterford couple lured her out of her house with a ruse about a broken-down car and strangled, beat and electrocuted her.

A fellow inmate told police that Patricia Prue, 33, said they chose Jenkins because of her gorgeous blond hair and because she felt socially snubbed by Jenkins, the affidavit said. The inmate said she overheard Prue saying that Jenkins wouldn’t recommend Allen Prue, 30, for snowplowing jobs and that they sexually assaulted her.

Police also said they found a ripped-up note that Patricia Prue had written in jail with the phrases “We picked her because,” ”sexually attracted” and “It was fun.”

The latest news shook family and friends of Jenkins, a science teacher at the St. Johnsbury Academy and devoted mother of a 2-year-old boy.

“What we feel is rage and anger and pain and sadness, sickness, empty,” said Eric Berry, of Lyndonville, who is married to Jenkins’ cousin. He and his wife attended today’s arraignment.

“Nothing is going to bring Melissa back so therefore there’s no justice,” he said. “We’re just trying to work through this as a family.”

Jenkins’ toddler son was found sleeping in her abandoned car on a remote road near her home the night police say she was abducted.

Police say Allen Prue had plowed Jenkins’ driveway a couple of years ago. A friend of Jenkins told police that he had asked Jenkins out a couple of times and that she felt uncomfortable around him, according to earlier court documents. She stopped having him plow, and in autumn 2011 he showed up drunk at her home asking if he could plow her driveway the following year, an affidavit said.

The night Jenkins disappeared, her former boyfriend told police she called him saying that she had gotten a weird call from a couple who used to plow her driveway and she was going to help them. She wanted someone to know what she was doing, the documents say.

Allen Prue’s mother and sister, who attended Tuesday’s arraignment, declined to comment.