beneficiary change on life insurance policy

My wife and neighbor have been friends for over 15 years. Our neighbor changed the beneficiary on his life insurance policy from his nephew to my wife in september of 2009, making her sole benficiry. The nephew has power of attorney. The neighbor has terminal cancer and is unfortunatley fading fast. He has plenty of money to get him to the end of his journey.My question is in the state of California can the nephew change the beneficiary or cash the policy out claiming to use it for his uncles expenses?