That isn't their point anyways.
Anyone who looks at crime rates without those factors is either a 5 year old or simply an idiot.
The death penalty isn't necessarily going to lower the crime in high crime rate countries, it doesn't have nearly as much of an effect as the social and economic conditions in a place at a given time. Therefore, a place having a high homicide rate is really irrelevant to whether they should implement capital punishment.
Read what i write for once.
Countries like egypt needs the death penalty because it reached incredably high rates in all sorts of crimes and cant be contained by any other means.
Thats why you have things like martial law, and death penalty. When things get out of control or crime rate sky rockets, you need to use the very last thing to push crime down, and that is fear.
Is it tried before ? Yes, countless times, and in our age, i already mentioned that we already used it and it worked, in 3 different countries.
There are no predetermined "stages" a society goes through in behavior.
There are stages for all reformation programs to go through, and its long term.
Thats why when you have conditions like in Egypt, long term will mean you'll have a few million victims on your hand before you're done with preparing basic needs for any supposed program.
That, as you might imagen, is a stupid solution to wait for without doing any short term and direct action, which is usually by applying strecter and harder laws and more security to prevent crime.