Earlier quoted context omitted.
Wow this data is going down but look at this: Half of males (50%) and more than half of females (59%) in federal prison were serving time for drug offenses on September 30, 2014.
If someone is convicted of killing 2 people and also of manufacturing and possession of 5 pounds of meth, do they fall into the same category of "serving time for drug offenses"? I think the category people are actually interested in is how many people are incarcerated for only drug-offenses and only minor (possession, not drug-kingpin) ones.
The above stats are current prisoner charges, my assumption is murderers wouldn't be out to get a charge by making meth. But who knows they seem to be harder on drugs than real violent crime at times (80s especially right after the DEA was created by Nixon in '75).