Special Judicial Magistrate Preeti Singh granted the permission on an application filed by CBI about two weeks back.
However, date of narco test is not finalised.
Earlier, the CBI had taken a written permission from the Rajesh and Nupur Talwar for conducting the tests on them.
Narco analysis involves psychotherapy which is conducted while the patient is deeply sedated with medication so that inhibitions are reduced and responses more truthful.
The Ghaziabad court on Monday, Jan 4, heard the CBI's application, which said its probe team found fresh clues, requiring the Talwars to undergo narco tests.
14-year-old Aarushi and domestic help Hemraj were found murdered in her Noida house on May 16, 2008.