Well, I agree that there is a very serious problem, which certainly did not go away in 1960. (I thought 1960 was a curious cut-off point, as if this was a historic problem only of interest to academics studying the early C20, when actually it is a current issue.)
These figures illustrate that there has not been any progress since 1960, since the murder rate is the same sixty years later. Perhaps that was the point you were making.
My point is that the death penalty has never been a deterrent to murder. Over the periods we have mentioned the death penalty has been abolished in many countries with no discernible effect on murder rates.
The case for abolition has not been made here, but it has nothing to do with deterrence. In the UK it became morally repugnant to a large part of the population from which juries were drawn. Cases came to light in which innocent people had been hanged. Juries were reluctant to find accused people guilty because they did not want to send people to the gallows; their only recourse was to acquit. A few notorious cases were heavily criticised in the press and in Parliament.