From what I know, this seems to be way more than Klein should have given him. A couple of years ago, before I had back surgery, my doctor gave me demerol shots so that I could walk without falling to the floor in pain (seriously). In one weeks' time, he gave me four shots. I called back the next week to see if I could get another one and he said no; that I had already gotten the max I could get. And I don't think he did that just to cover his ass. He knew how much pain I was in. I literally couldn't walk without a cane and, even then, it was "iffy". Something was pinching the sciatic nerve and pain would shoot down my leg to my toes and I would double over. I don't know what kind of pain MJ was in but, just from my experience, 51 doses in three months time seems like a lot. That would be 4 shots every week for three months.
However, I'm not sure how this would get Murray acquitted. Just because Klein gave him all of that demerol doesn't mean that Murray didn't act irresponsibly. It might show that MJ had a drug problem. Except that, if Klein loaded MJ up with demerol the day before and Murray was not aware of it, he might be acquitted due to ignorance. If I remember correctly, Murray didn't give MJ any demerol, did he?
So many "ifs".