1. Would the bodies potentially be radioactive?
I guess that depends on the way they were exposed to radiation. The rays (gamma rays) however wouldn't be enough to contaminate someone. You need some kind of stuff that emits those rays.
There are three types of radioactive radiation. Mind me, I'm not quite sure if I use the correct English terms, but you should find the right ones, if I made a mistake.
alpha radiation - when the radioactive element decays it emits an Helium atom. IT's range is very small, within inches. This kind of radiation is highly destructive and very dangerous, but a piece of paper is enough to shield it.
beta radiation - when the radioactive element decays it emits either an electron (very small corpuscle with a negative charge) or a positron (same thing but positive charge). The range of beta radiation is within meters. You would need lead to shield this type of radiation. So Kryptonite would be likely to emmit beta radiation.
gamma radiation - the radioactive element emmits a photon (light) with a very high energy. The range is endless, so to speak and you can hardly shield this type of radiation.
2. Would the police be able to figure that out before an autopsy? If so, how? Would there by some sort of sign on the body?
That would depend on the duration of exposure. There is a critical amount of radiation a person can tolerate. About 7 Sv (describes an amount of energy) would be instantally lethal for any human. I guess it would cause some kind of burns on the skin. If your 7 people were exposed to radioation for a couple of days or weeks even they would suffer of radiation sickness, meaning that they would loose their hair, suffer from diarrhea, nausea, vomiting and so on.
3. Once the police figured out that the bodies were radioactive, what would they do to ensure that no one was exposed to the radiation as they waited for the experts to arrive?
The best way? Staying away from them. The amount of radiation you're exposed to decreases with the distance.
4. What experts would they call?
Oh, good question. I guess physicians who deal with radiation regularly, physicists. I'm not sure.
5. At the autopsy, would the police be able to match it to a particular source of radiation? For example, kyrptonite poisoning v. poisoning from some sort of nuclear reactor.
Since there has to be some sort of radioactive stuff either on or inside those poor victims, I guess the police would be able to locate it. Kryptonite would make it pretty obvious. And I guess that a specialist could find out where the stuff came from by looking for the isotopes of the element. The number of protones is always the same in the same element, the number of neutrones isn't. I guess that different nuclear reactors would work with different mixtures of isotopes from the same element.
6. And could someone receive a deadly dose of radiation by be injected with something?
I guess so, but please don't ask me what that's supposed to be
