Gary sent this email....
Hi, My dog died in late febuary and I'm sure it was from a type of rat
poison due to symptoms found online and I have had the dog refridgerated
until today when I put him into a deep freezer due to warming
temperatures. I was wondering if a liver and blood tests for warfarin or
the other rodenticide bromadiolone would be detected after tissues were
frozen. This poisoning was as I'm almost %100 sure was done by my
landlord. I did not have the funds to have the necropsy done, and won't
untill a few months away from now.Due to the remoteness of my residence
and lack of any other homes in area and prior verbal threats made by
landlord and other proof, i highly suspect intentional poisoning. I had
read your blog and you offered to answer questions, so Can a necropsy be
done on toxicological tests?
Gary, I'm very sorry that you lost your dog. Unfortunately, it's going to be impossible to properly determine the cause of death in a situation like this. Even refrigerated tissues will deteriorate, especially over a few months. Believe it or not but frozen tissues can have even more damage. Even though you're preventing rotting of the tissues, the freezing process can cause significant microscopic damage, which is worsened with a thaw. If you wait another few months, the damage will be worse. Basically no pathologist will be able to accurately assess the tissues because the refrigeration and freezing have caused enough damage that it will be difficult to tell what happened as a result of these processes and what happened prior to them. This damage is also visible grossly, making it difficult for the vet performing the necropsy to tell what happened due to death, what was normal post-mortem, and what happened due the prolonged storage.
When we want to submit tissues for pathology review we use formalin, a preservative. Diagnostic labs always tell us not to freeze tissues due to the likely damage. If we have to submit a specimen too large to put in formalin, we have to send it same day or overnight and have it cooled but not frozen. Longer refrigeration or frozen samples will cause significant damage.
A necropsy might be able to see traces of rodenticide in the the digestive tract, as most of these poisons are distinctive in appearance. However, it can take days after ingestion before you will see symptoms, so there is a good chance that the causative agent already passed through the system and won't be visible. I'm not enough of a toxicologist or pathologist to be able to say if there will be detectable amounts of anticoagulant in the body, but I would doubt it because of the months-long refrigeration alone.
Even if you could absolutely prove the presence of these poisons, I doubt that you could prove who did it or where they came from. This would be especially hard considering the time that will have passed between the poisoning and when you may prove the cause of death. But that would be for a lawyer and not me to determine.