The sources said of the Rs 2.63 crore of alleged disproportionate assets which were inquired by the agency between 1993-2005, nearly Rs 1.4 crore are in the name of
Akhilesh Yadav's wife Dimple which had weakened the case.
Last December, the Supreme Court had directed the CBI to go ahead with the probe against Mulayam and his sons Akhilesh and Prateek but dropped the probe against Dimple saying that she was not holding any public office and was only a private person.
Exclusion of Dimple changed course of investigation as allegedly unexplainable assets were in her name, the sources said, adding that the ruling weakened the case.
