Lucille

I'm thinking that there may be some barriers in obtaining a theft conviction. Theft requires that you prove all the elements beyond a reasonable doubt. The element of intent has to have been there from the beginning and one has to prove that. If someone gets the property of another and only later decides to keep it, that is not theft, but perhaps conversion.
See how neatly Jay sets up a defense by saying, after he received the critters, that they have MBD. Because there were no pictures of the critters by the seller at the time of sale, those who are listening to the account of what happened in order to decide the case may believe there might have been MBD, and therefore there may be a reasonable doubt that there was an initial intent to deprive, and the idea to deprive came about only after Jay saw the alleged MBD.
I'm certainly not standing up for Jay, I'm just pointing out that I think there may be some practical problems here getting a theft conviction.
And of course there is still the unauthorized use to work through.