I might sound pretentious, but humans are way smarter than any other animal.
Not really. Humans are destroying the planet. And humans seem to have more issues among their own species than other animals do. Other animals don't kill each other for no reason (or at least not in the numbers we do...) or rape others or any of the number of ridiculous crimes humans do to others.
Humans may have intelligence but in no way are we smart. >.< So much of the stuff humans have discovered or created has been bent to be used in totally negative ways. Other animals, while they seem to lack the capacity (I say seem because we can't really determine much about other animals...) that we do, are smarter than us because they're not so self-destructive as humans are.
This isn't to say that I think humans should be the test subjects. Generally, the issue here is a population difference. There are significantly more of the animals generally used for testing. Rats, for instance; they outnumber humans by huge numbers. I know lots of illegal tests happen too on animals that don't have as big of populations...but we're going to ignore that for the sake of argument mostly because the number of these tests is actually quite low, probably enough to be completely negligible.
Also, another issue that comes into play when doing tests on human subjects on death row is the justice system itself.
It's long been known that the legal system is majorly flawed. Many people are placed on death row for crimes they didn't commit or for political reasons (see
this Wikipedia article about Mumia Abu-Jamal if you want an example...yes, I know...wikipedia...but its sources are cited and they check out so stfu lol).
Basically the problem comes down to ethics. And while I'm all for the fair treatment of animals and such, I do believe that with the few positives that the human race is trying to produce have to begin treatment on non-human subjects, if only for the issue of population control. There are many factors which come into play here. An animal subject can be placed under very strict control.
For instance, if a test causes a small animal like a rat to exhibit extreme rage, then it poses no threat to humans, as it can be dealt with. But if it was tested on a human and caused the same issue, then more lives are in danger. Or perhaps a test causes the subject to get a contagious disease. This could be a major issue in a prison environment. One extremely contagious disease could manage to wipe out an entire prison population. In a lab, under controlled conditions, the casualties would be the infected animal(s) and that's it.
There are reasons human testing is one of the final stages in development. It's simply way more dangerous to our population if we start there.