A Space Station 13 tricky situation

You are the Captain of the Space Station 13, and everything went bad very quickly. Most of the crew died, and it took you not so long to figure out that some people are not who they’re supposed to be (hence the bloody mess). Your task is to find out who is who in order to prevent the bad guys from reaching the escape shuttle.

There are 8 other crewmen with you: the Security Officer, the Medical Doctor, the Chief Engineer, the Cook, the Cargo Technician, the Botanist, the Janitor and the Clown (every station needs a Clown). You know that 4 of them are innocent, and that the 4 others are a Traitor, a Changeling, a Cultist and a Space Wizard. You also know for facts that:

• Everybody knows who is who (well… except you, the Captain, which is quite a shame).
• The only exception to the previous fact is that nobody knows who the Changeling is (except himself of course), and everybody believes the crewman the Changeling is impersonating is innocent.
• All innocent crewmen say the truth, or what they believe is the truth.
• The Cultist also says the truth (or what he believes is the truth), as part of a complicated ritual to summon N̻͔͓̳͇͖̝͠a̲͙̟͓̐ͧ̇̍̈ͥ̚͜r̲̠͇̲͈̐-͙̜͕̪͕͓͍̒̎̀S͈͕̅̾̕ͅi̙͋̎̒ͣ͗e̱͋̈́.
• The Traitor, Changeling and Space Wizard all lie (or what they believe is a lie).
• The Space Wizard will put a curse on you after you interrogated him, making you think the next crewman you interrogate said the opposite of what he actually said. For example, if you hear the crewman you interrogate just after the Space Wizard saying "The Janitor is a Cultist", what he actually said was "The Janitor is NOT a Cultist".

And this is what everyone said to you (in order of interrogation):

Security Officer: "The Medical Doctor is innocent."

Chief Engineer: "The Botanist is not innocent…"

Janitor: "The Clown is a Space Wizard!"

Cargo Technician: "The Chief Engineer is a Cultist!"

Medical Doctor: "The Cook is a Changeling!"

Clown: "The Janitor is a Traitor!"

Botanist: "The Security Officer is innocent."

Cook: "The Cargo Technician is a Traitor!"

Remember, your goal is to assert the identity of everyone, not just sort bad guys and innocents. The Traitor must be shot in the head, the Changeling burnt to ashes, the Cultist spaced and the Space Wizard properly dismembered.

_{If you liked this puzzle, try the rest of the story!}