As executor can I gain access to bank records of accounts held in joint tenancy between my Mother and brother?

Question

My mother left a will naming me as executor and splitting her estate equally between my brother and I. I have filed for Summary Administration for a mineral interest held in Oklahoma where I reside. Her only other assets are bank accounts held in joint tenancy with my brother in Arizona where she resided. The accounts were convenience accounts to allow him to pay her expenses, only her monies were deposited. He has not been forthcoming in allowing me to access statements for proving final payment of expenses etc. This may be laziness, he has not proven highly responsible with money and my mother had reservations on adding him to account. I would like to see records for peace of mind as much as any other reason. The amount of the estate is insignificant.

Matt Fleischer · Answer

Because the bank accounts were held in joint tenancy with your brother, both your mother and brother owned the accounts while your mother was alive. Upon your mother's death, the account became the sole property of your brother. Therefore, the account is not part of your mother's probate estate and you generally have no right to access it as the executor of her probate estate. 
 
All of that being said, you should consult an Oklahoma probate attorney. Depending on whether your mother's will was probated in Arizona, as well as other factors, you may be able to petition the OK court to force your brother to testify or turn over any records you may need.

Q: As executor can I gain access to bank records of accounts held in joint tenancy between my Mother and brother?