The toughest punishment would seem to require the most accurate judgment and as we know lots of prisoners come out free from a death row after DNA evidence was verified. The same evidence that FBI labors apparently
fucked up so much that one would think the error was systemic and not sporadic as one would hope. Taken this into account one would be forgiven to think that for crimes of lesser weight the procedures used were more relaxed.
This all is only for failures in the system that are failures also with current law. The whole deal or rot forever system is broken too. Not too mention that US systems are rather brutal - comparing to other countries considered civilized - less apparent violence in all other Western countries. DEA and all he corruption that is associated with it adds to the whole misery as are mandatory minimum sentences. You can look at specific failure points but how about looking at statistics and showing why US has to incarcerate and execute so many?
Tough on crime sells well. US citizens dislike liberals. Every criminal freed from prison that fails to stay straight is a reason to go for maximum. There is a lot of nonsense in US justice and penitentiary systems (as well as in law and law enforcement) and some people supporting this nonsense profit from it while having enough funds and not feel not enough restraint to use the wealth to support own position when law is created/revised. Who can blame them - it is American way....