A vet school may be able to determine some obvious things from a necropsy. The two avian viruses that are common to our backyard flocks have very distinctive indicators. Marek's virus causes obvious inflammation of the sciatic nerve, while leucosis virus causes a grossly enlarged liver. Also...
You must not freeze the body. It destroys tissues that need to be examined. Refrigeration is the way to preserve the body. But the necropsy should be done with 48 hours before serious degradation occurs.
Most chickens appear to have a seizure when they die. Furious wing flapping occurs as the...
If you haven't disposed of the body, it would be wise to find an animal testing lab and get a necropsy to confirm cause of death. Call your university extension office to find an agricultural lab.
Yes, it could be Marek's, but the symptoms can also be from toxin poisoning from petroleum...