A trial is under way for a husband, father and devout Christian who stands accused of shooting dead his wife and staging the crime scene to make it look like a suicide after failing to hire an assassin on the Dark Web.

Prosecutors allege that Stephen Allwine, 44, a deacon and church elder with the United Church of God, had at least three extramarital affairs with women he had met on the notorious cheaters' website Ashley Madison, and that he no longer wanted to be married to his wife, Amy Allwine.

Because of his position within the church, which views marriage as a lifelong commitment and prohibits divorce for its members, Washington County prosecutor Jamie Kreuser told the court on Tuesday that the defendant decided to rid himself of Amy by killing her following a botched murder-for-hire plot.

Amy, 44, a mother-of-one and a dog trainer, was found dead from a gunshot wound to the head inside the family's home.

Her husband told police he and their adopted son discovered the body and suggested that Amy had taken her own life, but police quickly determined that physical and ballistic evidence were inconsistent with a suicide.

Stephen, an information technology specialist, was arrested after a two-month investigation and was initially charged with second-degree murder, before a grand jury indicted him on a charge of first-degree premeditated murder. The upgraded count carries a mandatory life sentence.

Kreuser told the court on Tuesday that months before Amy's death, her philandering spouse had begun scouring the Dark Web in search of a hit man to kill his wife.