In ancient Greece and Rome, capital punishment of animals occasionally occurred.
In The Criminal Prosecution and Capital Punishment of Animals, by E.P. Evans (1906), the author collects and describes court cases in which animals have been named as defendants.
Theses cases include--chickens, rats, mice, bees, gnats, and in, 34 recorded cases, pigs.
The cases Evans describes are mostly in the very superstitious 15th, 16th and 17th centuries.
One of the earliest recorded cases, from France in 1266, is conducted in a matter-of-fact manner, hinting that these types of cases have a long history.
Secular trials were mostly held against domestic animals who had killed a
person. However, "wild" creatures like rats, field mice, eels, locusts
and ants, were often subject to the jurisdiction of the ecclesiastical courts.
In 1474, a chicken believed to be a rooster, laid an egg and was prosecuted by law in the city of Basel, Switzerland. For this “heinous and unnatural crime”, the chicken was given the death sentence, and publicly burnt alive in front of a crowd. 
In 1457, seven pigs (sow and 6 piglets) in Savigny, France, were tried for the murder of a five-year-old boy. The judge decided that while the owner should have been more watchful of his animals, the responsibility for the boy’s murder lay with the pigs.
The sow was sentenced to death, by being hanged from a tree by her hind legs. The piglets were freed on the "promise" of good behaviour.
Bartholomew Chassenée, a French jurist, made his reputation as a criminal lawyer in 1522, before the
ecclesiastical court of Autun, with his impressive defense of a group
of rats who were put on trial for destroying the barley crop of the
province.[1]
The court then ordered a second summons to be read, addressing all rats, from the pulpit of every local parish Church. The rats failed to appear in court for a number of appointed dates and Chassenée argued that it was due to fear of the cats in the region.
Such public trials probably restored the sense of moral and legal order in the minds of the people of the times and demonstrated the power of the Church and state.