Jerry Lee Stump of Caldwell and Kristen Irene Pickard of Garden City had the same victim, a teenager who was either 16 or 17 years old, said Tom Patterson, a detective for the Garden City Police Department.
Patterson said his department found out about the pair's alleged crimes Sunday morning through the Boise Police Department and arrested them later that day.
Other than that, Patterson wouldn't say much. He said investigators are trying to figure out how many times Stump, 34, and Pickard, 32, had sexual contact with the victim.
The maximum prison sentence for Stump's and Pickard's charge is life in prison.
According to state records, Stump was convicted in 2008 of possessing sexually exploitative material involving a child. He was sentenced to a prison term of 2 to 10 years.