lung fibrosis, morphine, would he of been 'of sound mind'?

my uncle died of fibrosis of the lungs. while he was in hospital, roughly about six hours before his death, he made a will making someone who was not family, or even a close friend a beneficiary of his entire estate. this beneficiary just happened to visit him on the day of his death, were we suspect he has 'influenced' my uncle into making a will. to leave his entire estate to this man was completely out of charactor and unrealistic, as he allways made it common knowledge to everyone that knew him that he was leaving everything to his neice, he even told a close friend this the day before he died. he was under the influence of morphine and possibly other drugs, and couldnt catch his breath at all. please could someone with medical knowlege advise me, would he of been 'of sound mind' to make a will? i want to be sure before i contest the will.