In 2000, the husband, Kunal Bose, had left his Gariahat residence in south Kolkata for dinner, but did not return and his body was found later.
Kunal's mother Anuradha, had accused Kunal's wife Aparajita of conspiring to kill her husband with an alleged associate Nantu Roy.
Aparajita had been sentenced to life imprisonment along with Roy for conspiring to kill Kunal, by the Additional Districts and Sessions Judge Alipore in 2003.
Aparajita, who was arrested in 2000 after the murder was in jail for 13 years.
A division bench comprising Justices Asim Roy and Suman Baidya today acquitted Aparajita, a mother of two children, observing that no proof of conspiracy was established against her.