The words "beyond a reasonable doubt" carries a ton of weight. Having gone through the legal system I will tell you a person facing trial would not want anything but a unanimous decision. That one hold out juror member may have a point that no other juror examined.
-------------------
To the point of this thread....I do feel the cop should have been convicted of manslaughter.
Moreover, I don't think manslaughter should have life attached to it. For example, what if you are driving, not drunk or high, have a blow out on your tire that causes an accident and someone dies. Why should you spend the rest of your life in prison because each time you come up for parole the family of the deceased says you should stay in jail.
That's just one example...
More on this case I wonder if the daughter was present when he killed the young man and I would really like to know what she said.