Humans make the results more accurate.
Consider the shoe bomber, the underwear bomber, Manson, the guy known as BTK (for "bind, torture, kill"), the Fort Hood shooter, and those guys that raped girls in Connecticut and then burned down the house with them inside. There are enough awful people that we have no shortage of humans for medical experiments.
I would have no qualms about performing the experiments. We can implant wires into their brains, give them harmful drugs, whatever... Except for the Fort Hood shooter, we can use these prisoners to test for methods to treat spinal injury. (we break their neck, wait the average amount of time it takes to reach a hospital, then try the experimental treatment) We can use them to test saving people who fall through ice. (dump them in, wait, attempt treatment) We can use them to test treatments for severe burns. (burn them, wait, attempt treatment)
Want to test something less serious, like household products? Sure, we can do that too. Strap them down, pin back their eyelids, and spray away. Whatever you like: perfume, ant spray, truck bed paint, engine degreaser, dishwasher detergent, laundry detergent, oven cleaner, drain unclogger, etc.