Halirrhothius or Halirrhothios (Greek: Ἁλιρρόθιος) was the son of Poseidon and Euryte (or Bathycleia[1]) in Greek mythology. When Halirrhotius raped Alcippe, Ares's daughter by Aglaulus, Ares murdered him. Ares was tried in a court made up of his fellow gods, the first murder trial in history. The trial was held atop the Acropolis of Athens, on what became known as the Areopagus. Ares was acquitted.[2]
In another version of the myth, Halirrhothius was sent by his father to cut down the olive that had grown out of the spear of Athena. As he raised his axe, it fell out of his hand and mortally wounded him. The olive was called "fatal" from that circumstance.[3]