My mother died leaving everything to my father. However, my oldest sister was on the checking account 2 years prior to my mothers passing. My father died 8 months after my mother. My sister's name remained on the checking account and she continued to use funds with no accountability. She was not the executor of the estate.
Was this proper according to Louisiana Law? Or should the checking account have been frozen on the death of my father?
She changed the password to the account so that no one else could view any activity on the account. Three of the Six children have had no communication from the others. They have the power and the money because we have been kept in the dark and refuse to answer any questions. Please can you shed any light on this. Five days after my father was dead they spent $600 and claimed it was for medication. That is ridiculous!!

Talk to the executor/lawyer who wrote his will and possibly your own lawyer, if a lot of money is in the account.
Both how the joint account were set up and what the will said need to be known. Was there a will?
In general, without searching LA law because this subject gets complicated, if 'joint tenants,' the sister can continue to spend. If tenants in common, she can't. The bank would most likely have asked your father what he wanted when the joint account was set up. The will should specify what he wanted upon his death.

A daughter was most likely involved in care that took a lot of her time, could be owed reimbursement, could have deposited some money of her own, and may be settling bills in arrears, as she should. We can't speak to whether she is spending when she shouldn't. Ask the executor for starters.

Yes, it all depends on how it was set up, many people use this as a form to transfer money to another person without it going into the estate or though probate.

If she was a owner with right of survival then upon the death of the other owner , she became the owner and the money was hers.