In March 1969, Ronald Ridenhour, an ex GI, having heard of what had happened in My Lai, decided to report the incident to the US authorities. At that time the case was transmitted to the Inspector General of the army for investigation. It was then subsequently committed to the army’s Criminal Investigation Division.
Parallel to this, the Defence Department had held its own investigation. These proceedings culminated in a report (the Peers Report), which recommended prosecution for several soldiers and officers – notably for incidents of murder and rape.
On 5 September 1969, Lieutenant William Calley was charged with premeditated murder of 22 people and of one case of attempted murder against a child of two years of age. His sentence was pronounced in application of Article 118 of the Uniform Code of Military Justice (Article 118 – Murder: Any person subject to this chapter who without justification or excuse unlawfully kills a human being when he — 1) has a premeditated design to kill, 2) intends to kill or inflict great bodily harm, 3) is engaged in an act which is inherently dangerous to others and evinces a wanton disregard for human life; or 4) is engaged in perpetration or attempted perpetration of burglary, sodomy, rape, robbery, or aggravated arson, is guilty of murder, and shall suffer such punishment as a court-martial trial may direct).
He was found guilty on 29 March 1971 and sentenced to hard labour for life and dishonourably discharged from the army.
Calley filed an appeal against his conviction.
On 21 December 1973, the United States Court of Military Appeals handed down its verdict in the case. It reiterated that American Military Law had long considered that the execution of a prisoner putting up no resistance was murder. Rather than systematically executing all of the villagers, Calley should have freed those amongst them who were obviously civilians and arrested those who could be suspected of being combatants. Even the hostile acts – which reportedly were committed by some of the people before their arrest – did not justify their execution.
The Court of Military Appeals also judged that Calley could not invoke in his defence that orders were received from his superiors in order to be exonerated from his criminal responsibility. Indeed, an act committed in conformity with an illegal order is not subject to punishment, except:
1. If the accused knew that the order was illegal: in such a case the personal character of the accused must be taken into account (education, hierarchical level, experience in the field, etc.), or
2. If someone of common sense and understanding, would have known, in the same circumstances, that this order was illegal: in such a case, the assessment would no longer be focused on the personality of the accused but on an abstractly defined standard.
In the case in point , the Court judged that the order given to kill children and unarmed civilians who were incapable of offering resistance, was very clearly illegal. Any person “of common sense and understanding” would have realised this. It was even possible to be more demanding of Calley in this respect, in view of his grade and experience.
As a result, Calley’s appeal was rejected.
Subsequently, after a series of reviews of his sentence, he was released on parole on 9 November 1974. His imprisonment had lasted for only 3 and a half years.