Whether or not a crime has happened with respect to the joint bank account that you have written about is beyond my ability to render an opinion to for the simple fact that I would need an accounting of fund withdrawals on dates and amounts.Once you ascertain from an accounting of funds withdrawn and by whom and for what purposes, you will be in a better position to see if any impropriety has happened with respect to the bank account you are writing about. You need to go to the bank where the account is located and ask for a register of all transactions within the needed time period.