(CBS/AP) KANSAS CITY, Mo. - Kansas City police plan to re-interview Lisa Irwin's two older brothers Friday using a specially trained social worker as part of their investigation into the infant's disappearance three weeks ago, The Kansas City Star reported Wednesday.
Police spokesman Capt. Steve Young said police also planned to collect DNA from the boys, ages 5 and 8, to compare to unknown DNA found during the investigation. Such samples can be obtained using a cotton swab inside the mouth.
Police said they hadn't been able to talk to the boys since Oct. 4, when parents Deborah Bradley and Jeremy Irwin reported 10-month-old Lisa missing. The boys are Bradley and Irwin's sons from previous relationships.
Police have said they have no suspects in Lisa's disappearance, though investigators have cleared hundreds of tips and leads and have searched the family's home, several wooded areas near the home, a landfill and a nearby industrial park.
Cynthia Short, the family's attorney, said Wednesday that police recently asked to interview the boys a second time and the parents "have had to weigh the best interest of their small children against the desire of the law enforcement to bring their boys in for a second interview."
The couple chose to allow the second interviews after they were assured they "would be done in a safe place and would be done by a specially trained social worker," Short said.
Linda Cordisco Steele, a child forensic interview specialist with the National Children's Advocacy Center in Huntsville, Ala., said while she was a "little bit surprised" that police had not talked to the boys since Oct. 4, there are no strict guidelines about how much time should elapse between such interviews.
"The thinking is the closer to the event and the closer together the interviews the more likely the information is not going to be lost or forgotten or contaminated," she said.
More interviews could be warranted if the investigation is active "and things come up," she said.