An American couple married for just three weeks lured a man to his death with a Craigslist ad because they wanted to kill someone together, police said.

Elytte Barbour told officers that he and his wife Miranda had planned to kill before but their plans never worked out until last month when Troy LaFerrara responded to an online posting that promised companionship in return for money.

His body was found on November 12 in an alley in Sunbury, a small city north west of Philadelphia.

The couple had recently moved to nearby Selinsgrove from North Carolina.

Mr Barbour, 22, and his 18-year-old wife face criminal homicide charges in connection with the death.

Mr Barbour told investigators that he hid in the back seat of the couple's SUV as his wife picked up Mr LaFerrara at a shopping centre on November 11.

He told police that, on his wife's signal, he wrapped a cord around Mr LaFerrara's neck, restraining him while Mrs Barbour stabbed him.

The 42-year-old, from Port Trevorton, Pennsylvania, was stabbed 20 times, police said.

Mrs Barbour initially denied knowing Mr LaFerrara, but her story evolved as investigators gathered evidence, including the discovery that the last call received by the victim's mobile phone was made from her number, according to a police affidavit.

The affidavit said Mrs Barbour acknowledged meeting the victim in Selinsgrove and driving with him to Sunbury, where they parked.

She said Mr LaFerrara groped her and she took a knife from between the front seats and stabbed him after he put his hand around her throat.

Police said Mrs Barbour had told them she purchased cleaning supplies at a department store after stabbing Mr LaFerrara, then picked up her husband and took him to a strip club for his birthday.

However, Mr Barbour told officers it was he that had purchased the cleaning products, an account investigators said was backed up by surveillance footage.

Following his wife's arrest, Mr Barbour told a local newspaper that his wife, whom he married on October 22, regularly hired herself out as a "companion" to men she met on various websites, a business venture he said he supported because it did not involve sexual contact.

Mr Barbour said his wife made anywhere from $50 to $850 for meeting men for such activities as having dinner or walking around.

The ads she placed on websites including Craigslist all said upfront that sex was not part of the deal, he said.

"She is not a prostitute," he told The Daily Item. "What she does is meet men who have broken marriages or have no one in their lives and she meets with them and has delightful conversation."

Sunbury police chief Steve Mazzeo told The Daily Item that investigators will also be looking into the death of a man with whom Mrs Barbour has a one-year-old child.