Madhvi, a former CPI(M) MLA, told PTI she respected the court and it seemed that the prosecutor may have erred in placing facts before the Patna High Court that led to the acquittal of Yadav and two others.
Stating that there was sufficient evidence in the murder case, Madhvi said she will approach the apex court against the acquittal.
Her son Amit also said the family would move the Supreme Court after going through the detailed court order.
The court also acquitted them of all charges in connection with the killing of Sarkar nearly 15 years ago.
Sarkar was shot dead by unidentified persons in Purnia district on June 14, 1998.