There is a big difference between potassium chloride in salt subsistute and potassium chloride as used in lethal injection–namely, injection. The same amount of potassium spread over time doesn’t pose the danger that it does all at once. In fact, there have been a few tragic cases where a nurse goofed up and injected potassium chloride into the IV hose instead of the bag. In the bag it was supposed to help the heart. The same dose in the hose killed.
This is a column by Cecil: http://www.straightdope.com/columns/991217.html
and should be moved to Comments on Cecil’s Columns.
Jill
And is hereby so moved.