Medina denied giving the orders to Calley during his court-martial, and only admitted to being a part of the incident later. Medina's defense lawyers cooked up a sickeningly brilliant defense of his position. He claimed that while he had briefed his men on the possibility that there would be Viet Cong in the village of My Lai, he never gave any direct orders to kill Viet Cong, even though eyewitness accounts had him killing unarmed civilians.

It is directly contradictory, and it's widely considered a farce that Medina got off scot-free. In fact, no one got any punishment for the massacre except for Calley, who ended up only serving three and a half years on house arrest. Don't forget, this wasn't swept under the rug at the point of the trial, this trial was a huge deal to the American public and a source of colossal outrage. It was the proverbial "last straw" of the political victory of the Viet Cong/PAVN at Tet, and helped bring about the end of the American influence in the conflict.

http://law2.umkc.edu/faculty/projects/ftrials/mylai/myl_intro.html