Since the passing of my Father, my Mother is now writing bad checks. What can I do?

they were farmers he over seen everything,but she wrote the bills,however she has gone from 500+ acres prime ia. farm ground,several houses to living in a shack and the indivivual she is with is married and has really prospered since,do you think there is a case against him based on this brief infomation

If your Mom is of clear mind [thus no Alzheimer's/Dementia] there isn't much you can do. It's her money to do with how she pleases. If she is writing bad checks, that means she has no money in her checking account, or she doesn't understand how to balance a checkbook so not to make that mistake. Did your Dad handle all the money matters?