In court documents, Marks is charged with third-degree felony custodial interference across state lines for taking the boy from the home shared by the grandmother, Tammy Marko, and the boy's father, Brandon Marks.
The mother, whose custodial rights had been revoked by a judge in favor of the child's father, allegedly waited until the grandmother briefly left the room on Monday during what was supposed to be a supervised visit, and then fled with the baby.
Using the mother's cell phone number, Murray police pinged the device and were able to trace her course through Utah to Idaho and Montana en route to Spokane, where she has family and friends.
When the Spokane County deputy contacted Marks at the residence and she refused to turn over the baby, the deputy apparently decided not to attempt an arrest because he did not consider her to be a flight risk.
Bass said that complicating the issue was that Spokane County court officials had determined that Utah court-provided documents including the custody order, affidavits and an arrest warrant did not meet Washington state legal requirements for interstate service.
Bass said the Salt Lake County Attorney's Office and court officials in Utah were working with their Spokane County counterparts Tuesday afternoon to resolve the matter.
Attempts to reach Spokane County Sheriff's Office officials for comment were not immediately successful Tuesday.