In class, I suggested that perhaps, to understand medieval animal trials, one had to distinguish two types of guilt as applied to the animal defendants. The first type only concerns whether the accused in fact performed the deed in question, while the second type concerns whether the accused has a moral responsibility for doing that deed. I'm sure we all agree that an animal can be guilty in the first sense, but that the second sense is rather murkier. My thought was that maybe medieval courts distinguished between these two types of guilt—that they tried some or all animals with the end of determining their guilt in the first sense, while tacitly acknowledging that the second sense was less applicable to beastly defendants.
In this model of law, a convicted animal would be punished not in retribution for its moral failing, but because it was a member of society, and the preservation of societal order required that disruptors of that order be punished. (Note that I do not at all mean the "upsetting of social hierarchy" proposed in our reading, merely violation of the common peace.) Since the end of class, however, I have had doubts about whether my aforesaid hypothesis is actually any good. It would go some way toward reconciling the trials of animals with the thinkers who objected to the idea of animals' being able to commit crimes, yet there are various cases where such a model would not seem to fit.
There is the case of the sow whose piglets were spared "on account of their youth and their mother's bad example." Surely these can only be considered mitigating factors in that they mean the piglets could not have known better; they hardly affect whether or not the piglets ate of the child. Similarly in modern life, we are lenient to human offenders for their youth, but we would never think of refusing to replace a lightbulb because it burned out soon after we bought it. The piglets, then, must in some way be considered more like the juvenile offenders than like the lightbulb.
And again, there is the case of the man who had intimate relations with a she-ass. If merely the commission of the act were sufficient for conviction, the trial would have been a foregone conclusion. Yet, as witnesses testified to the jennet's good character, she was spared—again on grounds of moral responsiblity, not of mundane facts.
A new hypothesis which I think might cover all of these cases is as follows: perhaps the medieval idea was simply that, for every evil deed done, someone must be held morally responsible. Not every participant in the deed, but at least one. This would account for the immunity from prosecution of oxen and horses, since as we saw their owner is the one punished by the beasts' confiscation and auction. The owner, then, bears the moral responsibility. Pigs, probably for some of the reasons we discussed in class, were considered more independent agents—it was thus that they were so frequently held guilty on their own, and their owners not punished. In the case of the piglets, the sow was the one to bear the moral responsibility for the deed to which she had led them. (One may wonder what would have happened in court had the piglets done the deed on their own.)
I'm a bit happier with this hypothesis than with the last one, but it still doesn't account very well for the treatment of wild animals or the ecclesiastical actions against vermin. I wonder if any of you have thoughts in those directions?