Is it legally possible for me to claim a life insurance benefit if the named beneficiary was my mother and she is also deseased?

I am so sorry for your loss.  That would depend.  If your Mother died after the person for whom she was named the beneficiary then the policy would be part of her estate and distributed to her heirs.  If, however, she pre deceased the person for whom she was the named beneficiary then there are no rights of your mother's heirs -you - to inherit.  Good luck.