Can a Will be Overturned?

My father recently passed away. His will created a Trust that included 6 beneficiaries (one of which is the wife). The Will states that she is to be able to live the life that she has been accustomed to...until her death, and then the remainder to be split between the remaining Beneficiaries. The trust was to include a 1 million dollar life insurance policy, and approximately 1 million in assets. The wife is a Dr. My father died of Liver failure, due to Alcoholism. After they learned that he only had 72 hours to 2 weeks to live, the wife had his Insurance policy changed to her being the sole beneficiary, with no legal representation, and no "unbiased" medical professional present. Two days later, he was confirmed of "sound mind" by a medical professional, with a Lawyer present. His memory was "hit and miss" during this time. The courts had him Involuntarily submitted to rehab for 30 days, sometime earlier. Mysteriously, 5 days into his rehab he was released (most likely, through her Standing in the Medical Community). She has, over the last ten years, perpetuated his Disease by the purchase of alcohol for his consumption. There have also been, at least one, incident when the Sheriff's Dept. has been called to their Home for threats of violence. Also, two days after his death, she transferred $50,000 out of one of his Personal Accounts. Would this account for an act of Negligence, on her part? Could this be an opportunity to Overturn his Will? The state of possible Litigation is Arkansas.